Apparatus and method for manufacturing blanks for rings or tubular members

Abstract

A method for manufacturing a bearing ring blank, or a gear ring blank, or a tubular connecting member blank, comprises the steps of: a) providing a steel tube; b) dividing the tube into a plurality of slugs (30, 30'), each having an axially extending cavity therethrough; c) feeding the slugs (30, 30') to a die assembly (20) of a cold forming station, the forming station also having a punch assembly (10); d) dividing the slugs (30, 30') into a die assembly (20) of a cold forming station, the forming station also having a punch assembly (10); and subjecting the leading slug (30) to a closed forward extrusion through a die assembly (20), wherein a thrust applied to the trailing slug (30') by a pressing member (11) of the punch assembly (10) causes the leading slug (30) to pass through the die assembly (20) and deform into a blank (40), during which a restricting member (12) of the punch assembly (10) blocks the axial cavity of the trailing slug (30') and at least a portion of the axial cavity of the leading slug (30).

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates generally to the manufacture of annular or tubular members.

[0002] In a first aspect, the invention relates to the manufacture of components for rotary bearings and has been developed in particular for the manufacture of steel blanks used to obtain inner and / or outer rings for bearings.

[0003] In a second aspect, the invention relates to the manufacture of components such as gears and has been particularly developed for the manufacture of steel ring blanks used to obtain gears.

[0004] In a third aspect, the invention relates to the manufacture of connecting components for machine members and has been developed in particular for the manufacture of steel blanks used to obtain piston pins and bushings in general and to obtain bushings for catenaries and vibration dampers (such as silent blocks) in particular. [Background technology]

[0005] Bearing rings are usually obtained by hot forging operations, starting from a complete (solid) steel billet. Essentially, the starting piece is hot drilled to define an axially hollow cylindrical blank, which is then subjected to other processing operations, such as machining for material removal, track formation, heat treatment, and grinding. This processing technique makes it possible to obtain rings with good mechanical and operational properties, but it also involves a large amount of material scrap. It reduces the productivity of the machines used for hot forging, and the associated depreciation management costs are very high. Similar problems exist in the case of bearing rings obtained by conventional turning.

[0006] Similarly, gear ring blanks are typically obtained by hot forging, starting from a complete steel billet. Essentially, the starting piece is hot-drilled to define an axially hollow, cylindrical semi-finished product, or ring blank, which is then subjected to other processing operations, such as machining for material removal, tooth formation, heat treatment, and grinding. While this processing technique allows for rings with good mechanical and operational properties to be obtained, it also results in a large amount of material scrap. This reduces the productivity of the machines used for hot forging, and the associated depreciation management costs are very high. Similar problems exist with gear blanks obtained by conventional turning.

[0007] Mechanical connecting elements such as piston pins or bushings for catenaries or vibration dampers are distinguished by a longitudinally extending body with an axial through-hole. Piston pins are usually manufactured starting from a cylindrical, complete piece of steel, which is axially drilled by turning or forging. Bushings for catenaries or vibration dampers can be manufactured using similar techniques or by directly turning a tube of the appropriate diameter. The corresponding blank is then subjected to other machining operations, such as removal of the pedestal, end finishing, heat treatment, and grinding, as well as machining operations.

[0008] The above mentioned machining techniques make it possible to obtain tubular components with good mechanical and operational properties, but they produce a large amount of chips. The productivity of the machines used for turning operations is very low, while forging techniques can only be applied to components with small diameters (suggestively, an outer diameter of up to 30 mm). Summary of the Invention

[0009] The object of the present invention is essentially to overcome the above-referenced drawbacks and in particular to provide a method and an apparatus making it possible to obtain components chosen from steel ring blanks for rotary bearings, steel ring blanks for gears and blanks for tubular mechanical connection elements made from steel, in particular piston pins and blanks for bushings for catenaries or vibration dampers, which exhibit good characteristics of geometric precision and reliability and which can be manufactured at significantly lower costs compared to the referenced prior art.

[0010] This object and other objects that appear below are further obtained by the present invention by a method and apparatus exhibiting the features referred to in the appended claims, which form an integral part of the technical teachings provided herein with respect to the invention.

[0011] In short, the idea underlying the invention is to produce a blank for a rotary bearing ring, or a blank for a gear ring, or a blank for a tubular connecting member blank, by cold deformation of a cylindrical piece, which is obtained by simply dividing a starting tube, in particular a tube obtained by hot rolling, into a slug. In a preferred embodiment, the cold deformation of the aforementioned slug is obtained using the specific technique of contained forward extrusion of a tubular piece.

[0012] For this purpose, preferentially, slugs obtained by dividing a starting tube are fed to the die assembly of a cold forming station, where they are subjected to a closed forward extrusion and forced through the die assembly by a punch assembly, the thrust exerted on the trailing slug by the pressing member of the punch assembly forcing the leading slug through the die assembly and causing a corresponding deformation thereof into a blank of a ring or tubular member, while the aforementioned limiting member of the punch assembly closes the axial cavity of the trailing slug and at least a portion of the axial cavity of the leading slug.

[0013] A substantial advantage of the invention is that the semi-finished starting product for obtaining the slag consists of a simple tube, which does not need to have very precise geometric dimensions, i.e., can be manufactured with sufficient tolerances. In this respect, the method and device according to the invention advantageously allow the use of steel tubes obtained by hot rolling, which is usually distinguished by the inexact definition of the corresponding outer and inner diameters and the lack of concentricity between the aforementioned diameters.

[0014] A further substantial advantage of the present invention is represented by the considerable productivity that can be obtained by cold deformation of the material, i.e., by obtaining large quantities of machined pieces in a short time, which entails great savings in terms of equipment: on the one hand, only a minimum of equipment is required (punch and die assemblies), and on the other hand, the time for the wear of such equipment is very limited.

[0015] A further important advantage of the present invention is that it allows for the cold deformation of steels previously considered unsuitable for such type of cold working, which is typically the case for bearing steels, particularly 100Cr6 steel.

[0016] A further important advantage of the present invention is that it allows rings having larger outside diameters and thicknesses to be obtained by cold working than would normally be possible with hot forging techniques.

[0017] A further important advantage of the present invention is that it allows tubular member blanks having large outer diameters and / or large thicknesses to be obtained by cold forming.

[0018] The blanks obtainable according to the invention are distinguished by a relatively higher stiffness than that of similar pieces obtainable using conventional methods, and also by the fact that the proposed type of processing allows for an optimal internal structure of the material to be obtained.

[0019] The geometric accuracy of the ring and / or tubular blanks obtainable according to the invention is in any case very high for both diameters of the final blank, which allows a considerable reduction in subsequent machining operations, as well as material savings (elimination of raw material and rejects). [Brief explanation of the drawings]

[0020] Further objects, features and advantages of the present invention will become clearly apparent from the following detailed description, taken in conjunction with the accompanying drawings, which are given by way of non-limiting example only. [Figure 1] 1 is a partial schematic view showing an apparatus for cold-forming a blank for a rotary bearing ring, or a gear blank, or a tubular member blank, according to a possible embodiment; [Figure 2] FIG. 10 is a perspective view showing a steel tubular slug used as a starting piece to obtain a ring blank according to a possible embodiment. [Figure 3] 1 shows a perspective view of a steel ring blank that can be obtained according to a possible embodiment; FIG. [Figure 2bis] 1 is a perspective view showing a steel tubular slug used as a starting piece to obtain a tubular component blank according to a possible embodiment. FIG. [Figure 3bis] 1 is a perspective view of a steel tubular component blank that can be obtained according to a possible embodiment; FIG. [Figure 4] 1 is a schematic top view illustrating a die assembly that can be used for cold forming a blank, according to a possible embodiment. FIG. [Figure 5] 5 is a schematic cross-sectional view of the die assembly taken along line VV in FIG. 4. [Figure 6] 6 is a schematic cross-sectional view similar to FIG. 5, showing a die assembly usable for cold forming of a blank, according to another possible embodiment. [Figure 7] 6 is a schematic cross-sectional view similar to FIG. 5, showing a die assembly usable for cold forming of a blank, according to another possible embodiment. [Figure 8]6A-6C are schematic perspective views of a die assembly of the type shown in FIGS. 4-5, but at different scales. [Figure 9] 1 is a schematic cross-sectional view showing a punch assembly that can be used for cold forming of a blank, according to a possible embodiment. [Figure 10] 1A-1C are schematic cross-sectional views showing the possible successive work stages envisaged for the manufacture of a blank for a ring or tubular element according to a possible embodiment. [Figure 11] 1A-1C are schematic cross-sectional views showing the possible successive work stages envisaged for the manufacture of a blank for a ring or tubular element according to a possible embodiment. [Figure 12] 1A-1C are schematic cross-sectional views showing the possible successive work stages envisaged for the manufacture of a blank for a ring or tubular element according to a possible embodiment. [Figure 13] 1A-1C are schematic cross-sectional views showing the possible successive work stages envisaged for the manufacture of a blank for a ring or tubular element according to a possible embodiment. [Figure 14] 1A-1C are schematic cross-sectional views showing the possible successive work stages envisaged for the manufacture of a blank for a ring or tubular element according to a possible embodiment. [Figure 15] 1A-1C are schematic cross-sectional views showing the possible successive work stages envisaged for the manufacture of a blank for a ring or tubular element according to a possible embodiment. [Figure 16] 1A-1C are schematic cross-sectional views showing the possible successive work stages envisaged for the manufacture of a blank for a ring or tubular element according to a possible embodiment. [Figure 17] 1 is a simplified block diagram showing a possible sequence of operations aimed at obtaining a blank for a ring or tubular element according to a possible embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0021] Reference to an "embodiment" or "one embodiment" within the framework of this specification is intended to indicate that a particular configuration, structure, or feature described with respect to that embodiment is included in at least one embodiment. Thus, phrases such as "embodiment," "one embodiment," "various embodiments," and "according to possible embodiments" that may appear in various places throughout this specification do not necessarily refer to one and the same embodiment. Furthermore, a particular configuration, structure, or feature defined herein may be incorporated in any suitable manner into one or more embodiments, including embodiments different from the illustrated embodiment. Reference numbers and spatial references (such as "upper," "lower," "top," and "bottom") used herein are provided for convenience only and thus do not define the scope of protection or the range of embodiments. In the figures, the same reference numbers are used to refer to similar or technically equivalent elements.

[0022] In this specification and the claims that follow, unless expressly stated otherwise or apparent from the context: the terms "blank", "ring blank", "gear ring blank", "tubular element blank", etc. are each intended to denote a cylindrical semi-finished element having substantially defined dimensions, which can be obtained through the device and method according to the invention and which is subsequently finished or machined in a manner known per se to obtain a semi-finished ring designed to be subsequently machined to obtain an inner or outer ring of a rotary bearing or to obtain a gear or a tubular element, for example a piston pin or a bush for a catenary or a bush for a vibration damper, the terms "tube slug", "tubular slug", "annular slug", etc. are intended to denote a tubular body that is substantially cylindrical and axially hollow, obtained for example by shearing a starting tube, and which is not necessarily subjected to a finishing machining operation before use, as envisaged by the present invention; - the term "tube" is intended to denote a substantially cylindrical, axially hollow body, not necessarily finished, which may be sheared or cut into slugs; The term "press" is intended to indicate a working machine designed to compress material being machined, capable of exerting high pressure on the material in order to deform it and give it a desired shape.

[0023] 1 shows a schematic representation of an apparatus that can be used to manufacture tubular connecting members, such as rotary bearing rings, or gear rings, or piston pins and bushings, according to the teachings of the present invention. In particular, the apparatus, generally designated 1, is used to obtain blanks for rings or tubular members. In the illustrated case, the apparatus 1 comprises at least one forming station. In a preferred embodiment, the apparatus further comprises at least one station for splitting the tube, preferably by shearing, into slugs. In a particularly advantageous embodiment, the apparatus 1 comprises one or more auxiliary systems selected from the following: - a manipulator system for transferring the slugs to the forming station -System for loading tubes a handling system for delivering the tube to a possible shearing station, and - An ejection system for removing the blanks from the device.

[0024] In the illustrated case, at least the aforementioned forming stations are implemented in a press 2, which has a generally known general construction, with the exception of what will be defined below as the "punch assembly" and "die assembly", generally designated 10 and 20 respectively in FIG. 1, which form part of the specific object of the present invention.

[0025] The assemblies 10 and 20, which will be described in detail with reference to Figures 4 to 8 and 9 respectively, are mounted on the press 2 in substantially coaxial positions, preferentially one on the movable part and the other on the fixed part of the press 2. In the example, the press 2 is a horizontal press, although in principle the use of a vertical press in other embodiments is not excluded.

[0026] In the example shown, press 2 comprises a load-bearing structure, generally designated 2', supporting a guide 3 along which a slide or ram 4 is slidably mounted. Slide 4 is translatable in a reciprocating motion, as indicated by arrow F, via an actuating assembly 5 carried, for example, by a cross member 6 of the stationary structure of press 2. Actuating assembly 5 may be of a known type (e.g., a piston-driven hydraulic actuating assembly or a cam-driven mechanical actuating assembly) suitable for generating sufficient closing forces, suggestively in the range of 50 to 500 tons, between assemblies 10 and 20. In this example, the punch assembly 10, as previously described, is fixedly associated with slide 4, while die assembly 20 is associated with structure 2', thereby providing relative motion between the two assemblies.

[0027] Preferentially, a passage 2a is defined below the die assembly 20 of the structure 2', through which the blanks obtained by machining in the press 2 can reach an unloading or discharge area 7. The unloading area 7 may form part of a discharge system and preferably comprises a conveyor suitable for transporting the blanks towards subsequent machining operations, for example turning and / or heat treatment and / or grinding and / or surface finishing operations.

[0028] As already mentioned, the device 1 may include a manipulator system. In the case illustrated in Figure 1, the press 2 is associated with a transport system 8 synchronized with the movement of the slide 4, this transport system 8 being constructed in a manner known per se to those skilled in the art and including pre-adjusted means for automatically positioning the rough starting piece to be machined in a position corresponding to the die assembly 20.

[0029] In various embodiments, the apparatus 1 is provided with a control system CS pre-adjusted to synchronously manage at least the operation of the press 2, i.e. the operation of its actuator assembly 5 and the operation of the transport system 8. In various preferred embodiments, the aforementioned control system CS also manages one or more further stations or auxiliary systems of the press 2 selected from those previously referred to.

[0030] For example, referring again to Figure 1, a separation station is indicated at 9 for dividing the metal tube T coming from the loading system generally indicated at 100 into slugs, this station 9 and this system 100 can be constructed by techniques known to those skilled in the art. The tube slugs obtained at station 9 constitute the rough starting pieces that are the subject of the processing that will be carried out using assemblies 10 and 20.

[0031] In various embodiments, station 100 thus receives starting tubes T, for example via a delivery system 9a of a concept known per se, which are then divided in a manner known per se and sheared in station 9, for example by a moving shear / fixed shear system, to obtain tubular slugs having substantially the same dimensions (i.e., outer and inner diameters) as starting tube T. By means of a manipulator or transport system 8, the aforementioned slugs are individually positioned in positions corresponding to die assembly 20.

[0032] Regardless of the manner in which the individual slugs are positioned in the die assembly 20, operation of the press 2, and thus the closing of the punch assembly 10 against the die assembly 20, significantly reduces the area of ​​the starting slug, thereby enabling a blank for a bearing ring or gear ring or tubular member to be obtained with clearly defined geometric dimensions.

[0033] FIG. 2 shows a schematic example of a rough starting piece to be processed in press 2 to obtain a ring blank for a bearing or gear, while FIG. 2bis shows a schematic example of a rough starting piece to be processed in press 2 to obtain a blank for a tubular component. As already mentioned, the starting piece, generally designated 30 or 30bis, essentially consists of a tubular or annular slug of a metallic material, in particular steel. Slug 30 or 30bis comprises a substantially cylindrical body having two substantially circular end faces 31 and a peripheral or outer circumferential surface 32a. A cavity 33 runs through the body of slug 30 or 30bis, which thus also defines a peripheral or inner circumferential surface 32b. The outer diameter A and inner diameter B of slug 30 or 30bis, i.e., the diameters of walls 32a and 32b, may be irregular and may be subject to sufficient tolerances, but are essentially predetermined. The slug 30bis in FIG. 2bis used to obtain the blank for the tubular member has a larger axial dimension L than the slug 30 used to obtain the ring blank.

[0034] In this regard, it should be noted that the body of the tubular slug 30 or 30bis is preferably obtained by shearing a starting tube formed by techniques known per se. Preferentially, the tube is formed by hot rolling, which is an improved and relatively inexpensive technique suitable for the processed steels used to implement the invention.

[0035] Although the end faces 31 of the slugs 30 or 30bis are substantially flat and parallel to one another after the division of the tube T, their inner diameters B may be somewhat irregular. This irregularity may be due to deformations caused by the shearing process or to the fact that the hot rolling process does not result in a precisely constant starting tube, especially with regard to its thickness, so that the slugs 30 or 30bis may exhibit considerable deviations in shape and concentricity between the circumference determined by the outer diameter A and the circumference determined by the inner diameter B, as illustrated in Figure 2 or 2bis. However, the device and method according to the invention advantageously allow the use of relatively irregular tubular slugs, i.e., tubular slugs that do not necessarily require preliminary finishing machining operations.

[0036] In various preferred embodiments, the starting tube T from which the slug 30 for the bearing ring blank is obtained has a high resistance to cold deformation, in particular about 65 kg / mm 2 The starting tube and thus the slug 30 are made of a steel having a tensile strength not lower than 100Cr6. A particularly suitable steel for implementing the present invention is one belonging to the group of bearing steels, such as annealed 100Cr6 steel. Naturally, other metallic materials can be used to obtain the starting tube and thus the slug 30, provided that the material used for the bearing ring exhibits good mechanical strength, wear resistance, impact resistance, and corrosion resistance, and ensures good dimensional stability.

[0037] In various preferred embodiments, the starting tube T for obtaining the slug 30 for obtaining the gear ring blank has a loading capacity of about 50 kg / mm 2 The gear ring is made of a steel having a tensile strength not lower than 16MnCr5 or 20MnCr5. Particularly suitable steels for carrying out the invention are those belonging to the group of case-hardened steels, such as 16MnCr5 or 20MnCr5. Of course, other metallic materials can be used to obtain the starting tube and thus the slug 30, provided that the material used for the gear ring exhibits good mechanical strength, wear resistance, impact resistance, and corrosion resistance, and ensures good dimensional stability.

[0038] In various preferred embodiments, the starting tube T for obtaining the slag 30bis has a flow rate of about 50 kg / mm 2 The starting tube and thus the slug 30bis are made of steels with a tensile strength not lower than 100 MPa. Steels particularly indicated for implementing the invention belong to the group of case-hardened steels (e.g., 16MnCr5 for piston pins), steels suitable for induction hardening (for catenary bushings), and low-alloy steels (for vibration damper bushings). Naturally, other metallic materials can be used for the manufacture of the starting tube and thus the slug 30bis, provided that the material used for the tubular connecting element of the type referred to exhibits good mechanical strength, wear resistance, as well as impact and corrosion resistance, and ensures good dimensional stability.

[0039] Figure 3 shows schematically an example of a blank for a bearing ring or gear ring indicated by 40, which can be obtained according to the invention, while Figure 3bis shows schematically an example of a blank for a tubular connecting member indicated by 40bis, which can be obtained according to the invention, where it is assumed that this blank is a piston pin, or a bush for a catenary, or a bush for a vibration damper (for example of the siren block type).

[0040] A blank 40 or 40bis, which can be subsequently finished by known techniques, may be obtained starting from a tubular slug of the type previously designated by 30 or 30bis, respectively.

[0041] The blank 40 or 40bis has two opposite end faces designated 41a and 41b, a peripheral or outer circumferential surface 42a with a diameter A', and a peripheral or inner circumferential surface 42b with a diameter B'. Like the starting slug 30 or 30bis, respectively, the blank 40 or 40bis also has an axial cavity 43, which is defined with a sufficiently high degree of precision as a result of the method according to the invention. Unlike the slug 30 or 30bis, the blank 40 or 40bis actually has a precise diametric dimension with precise peripheral concentricity determined by the diameters A' and B' as a result of the specific deformation method described below.

[0042] Roughly speaking, the outer diameter A' of the blank 40 or 40bis is clearly defined and significantly smaller than the outer diameter A of the corresponding starting slug 30 or 30bis, while the inner diameter B' of the blank 40 or 40bis is smaller than the inner diameter B of the corresponding slug 30 or 30bis, even if the dimensional difference between diameters B and B' is preferentially less than the dimensional difference between diameters A and A'. Furthermore, due to the cold deformation method envisaged by the present invention, the blank 40 or 40bis has an axial dimension L' that is longer than the axial dimension L of the corresponding tubular starting slug 30 or 30bis, respectively.

[0043] As will be seen below, end face 41a of blank 40 or 40bis, which is conventionally defined herein as the "upper face", has a slightly concave surface (by a few tenths of a millimeter, e.g., 5-15 tenths), while end face 41b, which is conventionally defined herein as the "lower face", has a slightly convex surface (by a few tenths of a millimeter, e.g., 5-10 tenths).

[0044] As previously mentioned, the concept underlying the present invention is to start with a tubular slug and significantly reduce the area of ​​this tubular slug (i.e., the area of ​​the annulus defined by diameter AB in relation to the annulus defined by diameters A'-B') to obtain a blank. According to the present invention, this reduction in area is obtained by a specific cold deformation technique, defined herein as "closed forward extrusion of a tubular piece." The reduction in area obtained according to the present invention, for example with bearing steel, is suggestively between 20% and 40%, while with case-hardened steel it is suggestively between 20% and 50%.

[0045] In conventional closed forward extrusion (known by the terms "closed forward extrusion", "trapped forward extrusion", or "closed-die forward extrusion"), a complete metal piece is partially forced through a thrust bushing into the orifice of a die having a diameter expansion smaller than the starting diameter. The piece is accommodated entirely in the die before extrusion takes place. The final piece has an increased overall length and deformed sections with reduced diameters. Closed forward extrusion, which can generally cause a major reduction in the area of ​​the starting piece, even up to 70% for suitable materials, is usually used to obtain complete components with axial sections of significantly different diameters connected to each other by radial surfaces. On the other hand, forward extrusion of tubular pieces is a technique in which a starting piece has an axial cavity, and a punch is inserted into this cavity from the same direction as the starting piece is fitted into the die, and at the moment of forward extrusion, this punch accommodates the inner diameter of the part to be extruded, and a bushing in the punch assembly pushes the piece out of the die.

[0046] On the other hand, the technique of closed forward extrusion of tubular pieces proposed by the present invention assumes the machining of an incomplete starting piece, i.e., a tubular piece, and the machined tubular piece pushes the preceding tubular piece through the area reduction and forming areas of the die assembly.

[0047] In various preferred embodiments, the starting tube T is subjected to a phosphating step before being divided into slugs 30 or 30bis. Alternatively, the slugs 30 may have to undergo such a step after the tube is divided, for example if the dividing of the tube into slugs is carried out in a purposefully designed device separate from the press 2. The phosphating step makes the slugs suitable for the subsequent step of cold deformation.

[0048] 4-8 show various views of an example die assembly 20 according to the present invention.

[0049] In the illustrated case, the die assembly 20 is constituted by a single body, but in other embodiments, the die assembly 20 may be formed of at least two pieces superimposed on one another, depending on the length of the tubular slug to be deformed or the length of the blank to be obtained. The body or bodies constituting the die assembly 20 may advantageously be made from special tool steel or hard metal.

[0050] 4, 5, and 8, the body of assembly 20 has an axial through-hole 21. The upper portion of cavity 21 forms an axially extending receiving area for slug 30 or 30bis, designated 22. This area 22 preferably has a constant circular cross-section and a diameter that is only slightly (a few tenths of a millimeter, e.g., 5-10 tenths) larger than the outer diameter A of the starting slug 30 or 30bis. This small difference in size between diameter A and the diameter of receiving area 22 is intended to facilitate insertion of slug 30 or 30bis into area 22 while avoiding excessive space that could result in undesirable lateral movement of material during pressing of slug 30 or 30bis.

[0051] In accordance with an important feature of the present invention, within cavity 21, immediately below area 22 for receiving slugs 30 or 30bis, is defined an area-reducing area 23 having a gradually decreasing diameter followed by a forming area generally designated 24 in FIG. 5.

[0052] The area-reducing region 23 is essentially defined by an annular band on the surface of the cavity 21, which may have a conical contour, as illustrated in FIG. 5, or a concave, curved contour, as illustrated in FIG. 6. In the case of a conical contour, the conicity may be indicatively between 10° and 20°. Alternatively, a concave contour may have a constant radius of curvature substantially equal to the difference between the diameter of the region 22 and the minimum diameter of the region 23. Naturally, it is possible to use a concave contour with approximately the indicated radius of curvature depending on the characteristics of the ring blank or the tubular member to be obtained. Thus, the contour of the area-reducing region 23 generally has a maximum diameter corresponding to the diameter of the receiving region 22 and a minimum diameter corresponding to the minimum diameter of the forming region 24.

[0053] In various embodiments, such as that illustrated in Figure 5, the die assembly 20 is sized for performing closed forward extrusion, i.e., has a receiving area 22 long enough to accommodate the entire starting slug 30 (or 30bis) even before it is pressed. Alternatively, in other embodiments, such as that illustrated in Figure 7, the assembly 20 is pre-tuned to achieve open forward extrusion, or has a receiving area 22 of a shorter length, such that pressing occurs with the slug (30 or 30bis) not entirely accommodated in the area 22 but at least slightly protruding therefrom. Of course, a concave profile of the type illustrated in Figure 6 may also be used when the assembly is pre-tuned to perform open forward extrusion.

[0054] As already mentioned, the area reduction region 23 is followed by a forming region 24, which has a minimum diameter that substantially corresponds to the minimum diameter of the area reduction region 23 and the outer diameter A' of the blank 40 or 40bis.

[0055] In various embodiments, the forming region 24 has a minimum inlet diameter and a maximum outlet diameter, the minimum inlet diameter corresponding to the minimum outlet diameter of the area reduction region 23, and the maximum outlet diameter being between the minimum outlet diameter and the maximum inlet diameter of the area reduction region 23.

[0056] In various embodiments, forming region 24 includes an inlet portion 24a of constant circular cross section followed by an outlet portion 24b of gradually increasing circular or conical cross section.

[0057] Inlet portion 24a has a length of a few millimeters (e.g., 1 to 4 mm) and a diameter substantially equal to the outer diameter A' desired for blank 40 or 40bis. Portion 24b, on the other hand, is slightly longer (suggestively at least twice as long as portion 24a) and its diameter is slightly increased, suggestively by a constant 1 / 10 to 2 millimeters. It should be noted that in Figures 4 to 8, the dimensions of portions 24a and 24b have been intentionally exaggerated to make the drawings easier to understand.

[0058] In operation, the material of the slug 30 or 30bis (here bearing steel or case-hardened steel) is forced to contract through the inlet portion 24a of the region 24 (acting essentially like a drawing plate) and then allowed to be released in the slightly wider portion 24b. In this way, the material does not slide significantly on the surface of portion 24b, thus preventing friction that could cause damage to the blank 40 or 40bis as it emerges, as well as avoiding the need to unnecessarily increase the thrust required to obtain the blank.

[0059] The forming region 24 is preferentially followed by a discharge region 25 of preferably constant circular cross section, with a diameter corresponding substantially to the maximum exit diameter of the portion 24b.

[0060] 9 shows a schematic cross-sectional view of a punch assembly 10 according to a possible embodiment. The assembly 10 comprises a pressing or pressure member, represented in the example provided by a cylindrical bushing 11, made, for example, from special tool steel, and having a substantially flat end face 11a (defined here as the "lower face" by convention). The outer diameter of the bushing 11 is slightly (a few tenths of a millimeter, for example, one to five tenths) smaller than the diameter of the receiving area 22 of the die assembly 20 and slightly (a few tenths of a millimeter, for example, one to five tenths) larger than the outer diameter A of the starting slug 30 or 30bis.

[0061] The assembly 10 further comprises a shape-limiting portion represented by a punch, here designated 12. The punch 12 has an elongated cylindrical body which, in the example shown, is partially housed in the cavity of the bushing 11 coaxially therewith and preferably in a fixed position relative thereto (unless, for example, a withdrawal system of the type referred to below may be provided). The body of the punch 12, made, for example, from special tool steel, has a respective portion 12a which projects axially from the face 11a of the bushing 11 and which, in use, is axially aligned with the cavity 21 of the die assembly 20.

[0062] The diameter of the main body portion 12a is smaller (by a few millimeters, for example 1 to 5 mm) than the inner diameter B' of the starting slug 30 or 30bis and is substantially equal to the inner diameter B' of the blank 40 or 40bis to be obtained, respectively. More precisely, due to the elastic response of the steel in the deformed piece, the diameter of the main body portion 12a is smaller than the aforementioned diameter B' by a few hundredths of a millimeter.

[0063] The diameter of portion 12a is evaluated taking into account the desired inner diameter B' of blank 40 or 40bis, the desired overall area reduction of slug 30 or 30bis undergoing deformation, and the fact that as the reduction in outer diameter occurs through regions 23-24 of die assembly 20, inner diameter B of slug 30 or 30bis must quickly confront punch 12 to prevent axial lateral squeezing / crushing that would prevent proper axial sliding of the steel. Similarly, the dimensions of the various regions of cavity 21 of die assembly 20 are selected depending on the desired outer diameter A' of blank 40 and the desired overall area reduction of slug 30 or 30bis undergoing deformation.

[0064] In the illustrated case, portion 12a of punch 12 terminates in tip 12b, which is preferably conical to facilitate insertion into slug 30 or 30bis. As will be described below, portion 12a may have a slightly conical shape to facilitate withdrawal of punch 12, particularly when assembly 10 is withdrawn from die assembly 20 (i.e., when slide 4 of press 2 in FIG. 1 moves away from fixed portion 2′). This obviates the need to rely on known synchronized withdrawal systems (e.g., of the timed stripper type, or the timed ejection type, or the timed knockout type) on the part of the punch, although this may be envisaged if necessary.

[0065] By way of indication, body portion 12a may have a length at least equal to the length of cavity 21 of assembly 20. More generally, it is sufficient for body portion 12a to be of such a length that, at the moment face 11a of thrust bushing 11 rests on the upper surface of slug 30 or 30bis housed in reception area 22 of die assembly 20, a portion of portion 12a engages both area-reducing region 23 and forming region 24.

[0066] As previously explained, in various embodiments, the press 2 of Figure 1 includes means 3-5 for reciprocatingly translating the punch assembly 10 relative to the die assembly 20. In the installed state, the bushing 11 of the assembly 10 is axially aligned with the cavity 21 of the die assembly 20 such that the smaller portion of the bushing 11 and the body portion 12a of the punch 12 can be positioned within the cavity 21 of the die assembly 20 and then withdrawn from the cavity itself.

[0067] 10 to 16 show possible processing sequences for press 2 using assemblies 10 and 20 of the type previously described. It should be noted that in the above figures, assemblies 10 and 20 are arranged vertically for illustrative purposes only, and for the same reason, assemblies 10 and 20, as well as slugs 30, 30' and blank 40, are shown in shortened length. Figures 10 to 16 illustrate the production of a bearing ring or gear blank 40 starting from slug 30, and it is to be understood that the production of a tubular member blank 40bis starting from slug 30bis is carried out in a similar manner.

[0068] For example, the slug 30 (or 30bis) obtained at station 9 in FIG. 1 by shearing the starting tube T is transferred by the system 8, together with the slide 4 of the press 2 in FIG. 1 moving towards the bottom dead center, into the die assembly 20, in particular into the position corresponding to the cavity 21 in its receiving area 22, as shown diagrammatically in FIG. 10. When the face 11a of the bushing 11 comes into contact with the upper surface of the slug 30 (or 30bis), the manipulator system 8 releases the slug itself, which is then pushed into the cavity 21 as shown in FIG.

[0069] Preferentially, the height of the region 22 is greater than the height L (FIG. 2) of the slug 30 (or 30bis), so that the slug 30 (or 30bis) is completely accommodated in the region 22. As explained above, in the illustrated embodiment, the area-reducing region 23 is defined by a band having a conical surface (FIG. 5 or 7) or a concave curved surface (FIG. 6). As already mentioned, the outer diameter of the slug 30 (or 30bis) is only slightly smaller than the diameter of the receiving region 22, which facilitates insertion and at the same time prevents undesired lateral movement of the slug material at the start of pressing, which would interfere with the process of closed forward extrusion.

[0070] As already mentioned, slide 4 of press 2 of Figure 1 moves punch assembly 10 into die assembly 20. As can be seen, body portion 12a of punch 12 enters the axial bore of slug 30 (or 30bis), and end face 11a of thrust bushing 11 presses against the upper surface of the slug itself, urging it through regions 22-24. Movement of assembly 10 is controlled so that forward movement is interrupted when face 11a of bushing 11 is in a position corresponding to the mouth of area-reducing region 23, as seen in Figure 12.

[0071] This results in a partial deformation of the slug 30 (or 30bis), which can be seen in FIG. 12. At this stage, the main body 12a of the punch 12 prevents the radial deformation of the inner slug 30 (or 30bis), i.e., its lateral collapse. As already mentioned, since the slug material must quickly encounter an insurmountable obstacle after entering the area reduction region 23, the inner diameter B of the slug 30 (or 30bis) is only slightly larger than the diameter of the punch 12. Therefore, the only passage for this material is shown by the regions 23-25 ​​not blocked by the portion 12a of the punch 12. Thus, the deformed material can fill these regions to form pieces whose geometric dimensions are very precise, even if the starting geometric dimensions of the slug 30 (or 30bis) are not precise. As can be seen in FIG. 12, at the end of the axial movement of the assembly 10, a portion of the material occupies region 23, and the remaining portion of the material engages regions 24-25.

[0072] As can be seen in FIG. 13, slide 4 then operates to retract punch assembly 10. It should be noted that the deformed material of slug 30 (or 30bis) is securely gripped within die assembly 20, thereby avoiding the risk of pieces lifting along cavity 21. Furthermore, as already mentioned, to prevent this problem, portion 12a of punch 12 may advantageously have a slightly conical shape, facilitating its sliding out of the hole in deformed slug 30 (or 30bis). Punch 12 may optionally be provided with a coating designed to improve its wear resistance, which may optionally help reduce friction and facilitate the removal of the punch itself from the deformed slug. If this is not sufficient, as already mentioned, press 2 may be equipped with a suitable synchronized withdrawal system on the punch assembly side. For this purpose, for example, the thrust bush 11 may be attached to a movable plate or support which, together with the bush 11 itself, is pressed for a short period of time during the return phase of the slide 4 and punch 12 by a known cam mechanism incorporated in the press 2.

[0073] At this point, the manipulator system 8, in the same manner as previously described, positions the subsequent slug, designated by 30' (or 30bis') in Figure 14, in the die assembly 20 and inserts it into the receiving area 22 together with the bushing 11. This is shown in Figure 15.

[0074] The punch assembly 10 is then brought to bottom dead center by the slide 4, as can be seen in FIG. 16, causing both partial deformation of the trailing slug 30' (or 30bis') and final deformation of the leading slug 30 and its ejection from the die assembly 20 through region 25.

[0075] In particular, the bushing 11 now pushes the trailing slug 30' (or 30bis)' downward, the underside of which exerts a corresponding pressure on the portion of the material of the leading slug 30 (or 30bis) that still occupies region 23. As the assembly 10 gradually advances, the material comprising the trailing slug 30 (or 30bis)' replaces the material of the leading slug 30 (or 30bis) in regions 23-25 ​​of the cavity 21. The leading slug 30 (or 30bis) is forced forward along the cavity 21, completing its forward contraction by completely passing through region 24, then entering region 25 and exiting the assembly 20 in the form of a blank 40 (or 40bis). The blank 40 (or 40bis) can then fall into the discharge area 7, for example, through passage 2a in FIG. 1.

[0076] 10-16 relate to the start of the method, resulting in the introduction of a third slug into the receiving area 22 of the die assembly 20 after a third retraction of the punch assembly 10. After a subsequent advancement of the assembly 10, said third slug pushes against the already partially deformed second slug 30' (or 30bis') to obtain a new blank 40 (or 40bis), and so on for further slugs and further blanks. To begin production, it may be wise to discard the first deformed piece 40 (or 40bis) exiting the die assembly 20, since this first deformed piece 40 (or 40bis) is in fact in a different state from all subsequent pieces (it has not encountered any preceding obstacles / pieces during forward extrusion).

[0077] As already mentioned, the blank 40 (or 40bis) emerging from the press 2 is then subjected to finishing processes known per se in the fields of rotary bearing ring manufacturing, gear manufacturing, or piston pin and bush manufacturing, which are not relevant to the present invention. As already mentioned, as a result of the specific method described, the upper surface 41a of the blank 40 (FIG. 3) or 40bis (FIG. 3bis) has a slightly concave surface, while the lower surface 41b (FIG. 3 or 3bis) has a slightly convex surface. To reduce the irregularity of the upper surface 41a of the blank 40 or 40bis, it is advisable to use a conical profile (FIGS. 5 and 7) in the area reduction region 23, suggestively with a slope between 10° and 20°, preferably about 15°, rather than a concave curved profile (FIG. 6). To eliminate the aforementioned surface irregularities of the surfaces 41a and / or 41b, the blank 40 or 40bis can be smoothed, in particular by conventional turning.

[0078] The proposed cold deformation technique allows for proper sliding of the material in the axial direction and complete filling of the regions 23-24 of the die assembly 20, thus providing a blank with high mechanical strength and very close tolerances, which can be sent to a subsequent finishing stage using significantly reduced thrust forces. The steel is deformed beyond the point of elastic resistance to obtain a blank with high stiffness (significantly higher than can be obtained by hot forging or conventional turning), with a high stiffness-to-weight ratio and optimal grain flow (non-destructive grain flow).

[0079] Using the method described above, field tests carried out by the inventors have shown that it is possible to cold-form ring blanks with high geometric precision and considerable mechanical reliability, with outer diameters ranging from 20 to 100 mm, thicknesses ranging from 3 to 25 mm (bearing rings) or 3 to 35 mm (gear rings), and lengths ranging from 20 to 75 mm (bearing rings) or 50 to 150 mm (gear rings), using annealed 100Cr6 steel (bearing rings) or case-hardened steel, in particular 16MnCr5 or 20MnCr5 (gear rings). The described method may also be used to obtain ring blanks with dimensions different from those tested.

[0080] Similarly, the method described above has enabled the cold forming of blanks for tubular connecting members to be obtained, which have high geometrical precision and considerable mechanical reliability, with an outer diameter of 20 to 80 mm, a thickness of 3 to 30 mm, and a length of 50 to 150 mm, using case-hardened steel (in particular 16MnCr5). However, the method described may also be used to obtain tubular connecting member blanks with dimensions different from those tested, and different steels may be used depending on the type of blank to be obtained (e.g., induction-hardened steel for catenary bushings or low-alloy steel for vibration damper bushings).

[0081] 17 shows, in a simplified block diagram, a preferred sequence of the steps of the method according to the invention. Block I shows the step of feeding and delivering the starting tube T to the separation station, where the tube itself is divided into slugs 30 or 30bis, as per step II. The slugs are then individually loaded into the die assembly 20, as per step III, for subsequent cold deformation by the assemblies 10 and 20, as per step IV. This is followed by the step of ejecting the blanks 40 or 40bis.

[0082] As has been seen, the various stages IV can preferentially be carried out in one and the same apparatus, if necessary. Stage II can be carried out, for example, by a shearing station (8) integrated into the same press (2) pre-adjusted to carry out the cold deformation of the slugs as in stage IV. This press (2) can advantageously comprise a system (100) for feeding and delivering the tubes to be sheared as in stage I, a manipulator system (8) for loading the individual sheared slugs into the die assembly as in stage III, and a system (7) for removing the blank from the press (2) as in stage V. As already mentioned, the apparatus or press is advantageously provided with a control system CS, preferably pre-adjusted to synchronize or coordinate the various operations referred to in stages I to V.

[0083] From the preceding description, the features of the present invention are clearly apparent, as are its advantages.

[0084] Naturally, details of the structure and implementation of the present invention may differ significantly from those that have been described and illustrated herein by way of example, without thereby departing from the scope of the present invention as defined in the following claims.

[0085] In the example described and illustrated above, it is considered that after the first cycle, in each cycle of the device 1, the slugs 30 (or 30bis) partially contained in the regions 23-25 ​​of the assembly 20 are expelled from the cavity 21. However, it is clear that the axial dimension of the region 25 may be such that in the second cycle of the device 1, said slugs 30 (or 30bis) are still within the region 25 or only partially outside the cavity 21, and then after the third cycle are completely expelled, and so on through the subsequent cycles of the device.

[0086] In the example provided, the device 1, i.e., the press 2, is configured to incorporate a station 9 for bench shearing the tube T, but this does not constitute an essential feature. In fact, in a possible variant embodiment, the tube T can be divided into slugs 30 or 30bis by a cutting or shearing station. Furthermore, the bench shearing or cutting or shearing stage can be obtained in a purposely provided device different from the press 2, and the press itself can then assume a system for transporting or loading the slugs 30 or 30bis in an automated manner known per se. In the case of cutting and shearing, the slugs can optionally be subjected to a peening process in order to eliminate any remaining burrs.

[0087] The device according to the invention may be provided in the form of a production line, the operations described being carried out by corresponding machine tools connected to one another by systems for delivering or transporting the tubes, slugs and blanks, respectively.

Claims

1. - rolling bearing ring blanks, - Gear ring blank - tubular connecting member blank A method for manufacturing a blank selected from the group consisting of: i) providing a hot-rolled tube made of steel, having an inaccurate inner and outer diameter and lacking concentricity between said inner and outer diameters, said steel being a bearing steel when producing a rotary bearing ring blank, and being a case-hardened steel when producing a gear ring blank or a tubular connecting member blank; ii) dividing the hot-rolled tube into a plurality of slugs (30, 30'; 30bis, 30bis'), each having an axial through-hole, each of the slugs (30, 30'; 30bis, 30bis') having irregular inner and outer diameters and having a concentricity error between the respective inner and outer diameters; iii) feeding the plurality of slugs (30, 30'; 30bis, 30bis') into a die assembly of a cold forming station, the cold forming station also having a punch assembly; iv) subjecting the slug (30; 30bis) to a closed forward extrusion through the die assembly, wherein the thrust applied to the trailing slug (30'; 30bis') by the pressing member of the punch assembly forces the leading slug (30; 30bis) through the axial through-hole of the die assembly and cold-deforms it into a blank, during which the limiting member of the punch assembly blocks the axial through-hole of the trailing slug (30'; 30bis') and at least a portion of the axial through-hole of the leading slug (30; 30bis); A method comprising:

2. A method as described in claim 1, wherein the slugs (30, 30'; 30bis, 30bis') separated from the hot-rolled tube in step ii) are supplied to the die assembly in step iii) without any preliminary finishing machining operations.

3. 2. The method of claim 1, wherein one of the hot-rolled tube and the slag (30, 30'; 30bis, 30bis') is subjected to a phosphating step before step iii).

4. The method of claim 1 , wherein the blank is subjected to a smoothing operation of at least one corresponding end surface.

5. 10. The method of claim 1, wherein step ii) is carried out in a separation station, wherein the hot rolled tube is subjected to one of bench shearing, cutting, or shearing.

6. The method described in claim 5, wherein the separation station is a shear station having a movable shear and a fixed shear.

7. Step iii) includes the direct transfer of each slug (30, 30'; 30bis, 30bis') from the separation station to the axial through-cavity of the die assembly by a transfer system. The method of claim 6.

8. 2. The method of claim 1, wherein step iii) comprises individually positioning each slug (30, 30'; 30bis, 30bis') by a transport system at a position corresponding to the axial through-cavity of the die assembly.

9. Step ii) is performed in a separation station, wherein the hot rolled tube is subjected to one of bench shearing, cutting, or shearing; 9. The method according to claim 8, wherein the transfer system picks up the slugs (30, 30'; 30bis, 30bis') separated at the separation station and transfers the slugs (30, 30'; 30bis, 30bis') to the position corresponding to the axial through-cavity of the die assembly in synchronization with the operation of the cold forming station.

10. Steps iii) and iv) are a) fitting said leading slug (30; 30bis) into the receiving area of ​​said axial through-cavity of said die assembly; b) axially approaching the punch assembly and the die assembly, b1) the pressing member exerts a thrust on the leading slug (30), and when the thrust begins, a first portion of the elongated body portion of the restricting member extends into the through-hole of the leading slug (30; 30bis) and a second portion of the elongated body portion extends into the area-reducing region and the forming region of the axial through-cavity of the die assembly; b2) the pressing member then pushes the leading slug (30; 30bis) from the receiving area through the area reduction area towards the forming area, At the end of said approach, said leading slug (30:30bis) has been deformed, its upper portion engaging the reduced area not blocked by the respective portions of said elongated body portion, and its lower portion engaging at least a portion of said forming area not blocked by the respective portions of said elongated body portion. axially approaching the punch assembly and the die assembly so that c) creating axial retraction between the punch assembly and the die assembly; d) placing said subsequent slug (30'; 30bis') into said receiving area; e) further axially approaching the punch assembly and the die assembly, wherein the pressing member forces the trailing slug (30'; 30bis') from the receiving area towards the forming area, so that at least a portion of the elongated body portion of the restricting member extends into the through hole of the trailing slug (30'; 30bis') and another portion of the elongated body portion at least partially engages with the through hole of the leading slug (30; 30bis), thereby causing the trailing slug (30'; 30bis') to move toward the leading slug (30; 30bis). bis), whereby an upper portion of the leading slug (30; 30bis) also passes through the forming area, and further axially bringing the punch assembly and the die assembly closer together so that at the end of this further approximation step, the trailing slug (30'; 30bis') has been deformed, its upper portion engaging the reduced area not blocked by the respective portions of the elongated body portion, and its lower portion engaging at least a portion of the forming area not blocked by the respective portions of the elongated body portion; f) repeating steps c through e for an indefinite number of subsequent slugs (30'); The method of any one of claims 1 to 9, comprising:

11. - Rolling bearing ring blank made from steel - a gear ring blank made from steel, - tubular connecting member blanks made of steel 1. An apparatus for cold-forming steel blanks selected from the group consisting of: a cold forming station having a punch assembly, a die assembly, and an actuation system for axially translating the punch assembly and the die assembly relative to one another, the die assembly having an axially through cavity, the punch assembly having a pressing member axially aligned with the axially through cavity of the die assembly; a supply device for supplying tubular steel slugs (30, 30'; 30bis, 30bis') having an axial through-hole and an outer peripheral surface, each having an inner diameter and an outer diameter, with a concentricity error between the inner and outer diameters, the supply device being pre-adjusted to automatically supply one of the tubular steel slugs (30, 30'; 30bis, 30bis') to the cold forming station at a position corresponding to the axial through-hole of the die assembly; Control system and Equipped with The axially extending through cavity of the die assembly is a receiving area defined by a first surface portion having a cylindrical shape of the axial through-cavity for at least partially receiving one of the tubular slugs (30, 30'; 30bis, 30bis'), the receiving area having a first diameter; a forming area defined by a second surface portion of the axial through-cavity having a shape complementary to the outer contour of the blank to be obtained, the forming area having a minimum diameter smaller than the first diameter; a reduced area region axially contained between the receiving region and the forming region, the reduced area region having an entrance diameter corresponding to the first diameter of the receiving region and an exit diameter corresponding to the minimum diameter of the forming region; and the pressing member of the punch assembly has an outer diameter slightly smaller than the first diameter of the receiving area, and further comprises a limiting member for engaging with the axial through-hole of one of the steel tubular slugs (30, 30'; 30bis, 30bis'), the limiting member including an elongated body portion protruding axially from an end face of the pressing member coaxially with the pressing member; After positioning at least one first steel tubular slug (30'; 30bis') or a subsequent slug at a position corresponding to the axial through-hole of the die assembly, the pressing member pushes the first steel tubular slug (30'; 30bis') from the receiving area toward the forming area, so that the first steel tubular slug (30'; 30bis') pushes the underlying second steel tubular slug (30; 30bis) or a preceding slug through the forming area. the control system is pre-adjusted to synchronize or coordinately manage the actuation system of the cold forming station and the supply device of the steel tubular slugs (30; 30bis) in such a way that the elongated body portion of the restricting member pushes the steel tubular slugs (30'; 30bis') toward the axial through-hole of the first steel tubular slug (30'; 30bis') and at least a portion of the axial through-hole of the second steel tubular slug (30; 30bis), The supply device comprises: a separating station for separating a hot rolled tube having an inaccurate inner diameter and an outer diameter and lacking concentricity between said inner diameter and said outer diameter into a plurality of said steel tubular slugs; an advancing system for advancing the hot rolled tube having the inaccurate inner and outer diameters and lacking concentricity between the inner and outer diameters toward the separation station; a transfer system for individually positioning each of the tubular slugs obtained at the separation station, each having irregular inner and outer diameters and having a concentricity error between the respective inner and outer diameters, at the position corresponding to the axial through-cavity of the die assembly; Equipped with Device.

12. The apparatus described in claim 11, wherein the separation station is a shear station having a movable shear and a fixed shear.

13. 12. The apparatus according to claim 11, wherein the transfer system is pre-adjusted to pick up one of the tubular steel slugs (30, 30'; 30bis, 30bis') coming out of the separation station and transfer the tubular steel slug (30, 30'; 30bis, 30bis') to the position corresponding to the axial through-cavity of the die assembly in synchronization with the operation of the actuation system of the cold forming station, without any preliminary finishing machining operations.

14. 12. The device of claim 11, wherein the area-reducing region has a conical contour with a slope comprised between 10° and 20°.

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