Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C23/00—Extruding metal; Impact extrusion
  • B21C23/001—Extruding metal; Impact extrusion to improve the material properties, e.g. lateral extrusion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C23/00—Extruding metal; Impact extrusion
  • B21C23/02—Making uncoated products
  • B21C23/04—Making uncoated products by direct extrusion
  • B21C23/06—Making sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C25/00—Profiling tools for metal extruding
  • B21C25/02—Dies

Definitions

• the present invention relates to a method of forming a flat object such as a sheet with a material having an ultrafine grain structure.
• references in brackets ([]) refer to the list of references at the end of the text.
• the ability to produce objects with an ultra-fine grain metal material is well established with severe plastic deformation methods such as equal-section angular extrusion, multi-axis deformation, extrusion-torsion, high-pressure twisting or rolling. multipass. Reducing the size of the grains to sub-micron or nanometric sizes has the effect of giving the metal material a high yield strength, satisfactory ductility, good resistance to fatigue, low temperatures and wear. This has been observed with many metals or metal alloys, whether steels, alloys based on titanium, aluminum, magnesium or lithium.
• microstructural changes are induced by very large plastic deformations imposed on a sample, a factor often greater than 3.
• the sample is pressed against a rough wall and rotated to a stop wall where it undergoes deformation by being pushed radially.
• a continuous shearing process is shown by publications [7] and [8] in which continuous web material is forced by a pair of rolls into a die with a side exit.
• the document [10] proposes a method in which part of an original part is cut on the surface and channeled in a radial space. Such a method does not make it possible to control the static pressure on the material and cracks can be created along sliding planes.
• the document [1 1] shows an extrusion process whose output is not symmetrical. Such a method does not achieve high levels of deformation.
• the aim of the invention is to propose a method for producing parts having an ultrafine grain microstructure, obtained by plastic deformation severe, which is quick to implement and can be implemented with moderate efforts.
• the subject of the invention is a process for forming a part in which a metallic material undergoes severe plastic deformation in order to confer on it an ultra-fine grain structure, into which a bar of said material is introduced into a matrix in an insertion direction, the matrix having an entry area with a cross-section with the section of the bar and an exit zone, the exit zone being oriented in a lateral exit direction with respect to the direction method for extracting the transformed material, the method being characterized in that, the matrix having an extrusion zone having the same direction as the input zone and of smaller size than the input zone in the exit direction in a ratio between 0.75 and 1 excluded, a transition zone comprising a transition face downstream of the exit zone and making the transition between the zone of In the extrusion zone, the extrusion zone is extruded, the transition face creating a pressure to push a portion of the material through the exit zone and extracting the converted material into sheet form.
• the method according to the invention makes it possible to obtain a very fine product even starting from a bar of large section.
• the efforts to provide are relatively limited since it is not necessary to deform the entire section of the bar, but only a part.
• the deformations obtained are of a great magnitude, so that the sheet obtained does not need to be worked again: an ultrafine grain structure is obtained directly.
• the process can be applied to many metallic materials. For example, pure metals or metal alloys, whether steels, alloys based on titanium, aluminum, magnesium or lithium, are used.
• the matrix is chosen so that: with:
• ⁇ section reduction ratio between the output section and the input section; the angle between the insertion direction and the transition face; t a / h where 2a is the width of the exit zone and h is the difference in size between the entry zone and the exit zone; and m is the coefficient of friction between the material and the transition face.
• the process according to the invention does not occur if certain conditions are not met. In particular, it would be possible to obtain a simple extrusion without the material flowing towards the exit zone if the hydrostatic pressure is not sufficient. The conditions described above are sufficient to ensure, even in the absence of back pressure, that the material flows to the exit zone to form the sheet. This relationship shows the conditions are more conducive if the reduction ratio ⁇ decreases, if the angle increases or if the ratio t decreases.
• the matrix and the back pressure are chosen so that: with:
• ⁇ section reduction ratio between the output section and the input section; the angle between the insertion direction and the transition face; t a / h where 2a is the width of the exit zone and h is the difference in size between the entry zone and the exit zone;
• m is the coefficient of friction between the material and the transition face
• p bp is the back pressure
• k is the elastic limit in shear of the material.
• FIG. 1 is a schematic representation of a longitudinal sectional matrix in which the method according to a first embodiment of the invention is implemented;
• FIG. 2 is a view similar to FIG. 1 for a second embodiment of the invention:
• FIG. 3 is a view of a detail of FIG. 1, also common to FIG. 2, without implementation of the method according to the invention;
• FIG. 4 is a view similar to FIG. 3 with implementation of the method according to the invention.
• FIGS. 5a and 5b are diagrams representing the operating conditions of the method according to the first embodiment
• Figures 6a and 6b are diagrams similar to those of Figures 5a and 5b according to the operating conditions of the second embodiment of the method;
• FIG. 7 is a diagram showing the evolution of a von Mises deformation for the sheet
• FIG. 8 is a side photo of a bar of which the sheet is manufactured.
• the sheet forming method according to the invention is implemented in a tool comprising a die 1 and a first piston 2 for pushing a bar 3 in the die 1.
• the bar 3 is made of a metal material with which it is desired to manufacture the sheet 4 after its structural transformation to obtain an ultrafine grain structure.
• the matrix 1, shown in FIG. 1 in longitudinal section in an insertion direction, comprises an input zone 1 1 able to receive a bar 3 of said material in the insertion direction F, a transition zone 12, a outlet zone 13 and an extrusion zone 14.
• the outlet zone 13 is oriented in a lateral outlet direction with respect to the introduction direction F.
• the extrusion zone 14 is in the extension of the zone of 1 1 entry, but with a dimension, considered as a height, less on the side of the exit zone 13.
• the respective heights of the extrusion zone 14 and the entry zone 1 1 are in a ratio between 0 , 75 and 1 excluded.
• the section is rectangular, the different areas of the matrix 1 having an equal width in the direction perpendicular to the cutting plane.
• the transition zone 12 has a transition face 120 downstream of the output zone 13 by making the transition between the input zone 11 and the extrusion zone 14.
• the transition face 120 is inclined at an angle has compared to the direction of introduction F.
• the first piston 2 has substantially the same section as the input zone 1 1 and is able to push the bar 3 in the insertion direction F through the die 1.
• the bar 3 also has a section adjusted to that of the entry zone 1 1.
• the bar 3 is introduced through the inlet zone 1 1, the first piston 2 is actuated, the bar 3 is extruded through the extrusion zone 14 at the same time as a sheet 4 by a portion of the material of the bar 3 which flows through the exit zone 13.
• the first piston 2 By forcing the passage of the bar 3 with a force F, the first piston 2 induces the passage of the initial thickness H 0 of the bar 3 at a reduced height of H 0 -h. In the transition zone 12, a large pressure is induced so that the outer portion of the bar 3 flows into the exit zone 13 and forms the sheet 4 with a thickness 2a. In fluent, the material undergoes severe plastic deformation, which gives it the desired ultrafine grain structure properties.
• the pressure applied by the first piston 2 P a can be expressed by: with ⁇ the section reduction ratio between the output section and the input section; The angle between the insertion direction F and the transition face 120; m is the coefficient of friction between the material and the transition face 120; k is the elastic limit in shear of the material; w r is a friction power of the bar 3 against the entry zone 1 1; and V 0 is the speed of movement of the first piston 2.
• a discontinuity of the velocity field is considered along an upstream line AB and a downstream line AC, in the sectional view. longitudinal.
• the point A is the vertex of the angle between the entry zone 11 and the exit zone 13
• the point C is the vertex of the angle between the exit zone 13 and the transition face 120
• the point A is substantially the intersection between the axis of the exit zone 13 and the projection along the insertion direction F of the vertex of the angle between the transition face 120 and the extrusion zone 14.
• FIG. 7 The evolution of e u , the equivalent deformation in the von Mises direction, as a function of t is shown in FIG. 7. This figure shows that for thin sheets and sheets, von Mises deformation is characteristic of deformation processes. severe plastic.
• the tooling is completed by a second piston 5 able to exert a counter-pressure on the end of the bar 3 in the extrusion zone 14.
• Thickness of the sheet produced 0.7 mm
• Size of grain in the sheet 610 nm.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Extrusion Of Metal (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

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Family Applications (1)

Country Status (3)

Citations (7)

• 2015
  • 2015-07-24 FR FR1557031A patent/FR3039084B1/fr not_active Expired - Fee Related
• 2016
  • 2016-07-19 EP EP16757278.3A patent/EP3297776B1/de not_active Not-in-force
  • 2016-07-19 WO PCT/FR2016/051847 patent/WO2017017341A1/fr not_active Ceased

Patent Citations (7)

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