CN113804559B - High-pressure torsion extrusion method for fine-grain sample - Google Patents

High-pressure torsion extrusion method for fine-grain sample Download PDF

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Publication number
CN113804559B
CN113804559B CN202111149561.4A CN202111149561A CN113804559B CN 113804559 B CN113804559 B CN 113804559B CN 202111149561 A CN202111149561 A CN 202111149561A CN 113804559 B CN113804559 B CN 113804559B
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sample
driving
lamination
anvil block
mandrel
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CN113804559A (en
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蒋理帅祎
方敏
张治民
王强
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North University of China
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/22Investigating strength properties of solid materials by application of mechanical stress by applying steady torsional forces
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0001Type of application of the stress
    • G01N2203/0003Steady
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014Type of force applied
    • G01N2203/0021Torsional
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/003Generation of the force
    • G01N2203/0032Generation of the force using mechanical means
    • G01N2203/0037Generation of the force using mechanical means involving a rotating movement, e.g. gearing, cam, eccentric, or centrifuge effects

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)

Abstract

The invention discloses a high-pressure torsion extrusion method of a fine-grain sample, which comprises the following steps: firstly, assembling a high-pressure torsion extrusion die, then after assembling all parts, putting a sample on a circular plane of an annular cavity, pressing down an upper anvil block, maintaining pressure, and starting a rotation control mechanism; finally, the driving mechanism drives the transmission shaft to rotate, and drives the lamination suite to rotate through the engagement of the driving gear and the driven gear, wherein the engagement ratio between the driving gear and the driven gearAnd angular velocityThe relation of (2) is:. The invention reduces the mechanical property and the tissue state of the sample prepared by the traditional high-pressure torsion processing, and the radial distribution of the sample is uneven, so that the linear speed at each point on the surface of the sample in the torsion process is consistent, and the prepared sample has better quality.

Description

High-pressure torsion extrusion method for fine-grain sample
Technical Field
The invention belongs to the technical field of metal plastic processing reinforcement, and particularly relates to a high-pressure torsion extrusion method for a fine-grain sample.
Background
The High Pressure Torsion (HPT) is used as a processing strengthening mode, and mainly comprises an upper anvil 1' and a lower anvil 2', wherein the upper anvil 1' is nested at the upper part of the lower anvil 2', a sample 3' is firstly placed between the two anvils, then the upper anvil applies pressure P, the lower anvil rotates to provide shearing force, the upper anvil descends and compresses the sample under the action of the pressure P, the magnitude of the pressure P is usually about several GPa, and shear strain is applied to the sample by the rotation of the lower anvil until the required strain amount is obtained.
From this conventional HPT process, it can be seen that HPT is an ultra-fine grain material obtained by the combined action of hydrostatic pressure, shear force and friction. However, according to the existing large number of experiments, for the samples prepared by the high-pressure torsion method of the conventional integral lower anvil, as shown in fig. 2, the linear velocity V increases linearly with the distance L from the center of the sample (hereinafter referred to as the center distance) due to the uneven radial distribution of the linear velocity of each point on the surface of the sample, which causes uneven tangential strain distribution to be applied to the sample; the surface hardness is increased along with the increase of the center distance L, and the surface structure of the sample is uneven after the traditional HPT processing, so that micro-galvanic corrosion is formed, the alloy dissolution is accelerated, and the corrosion resistance of the alloy after HPT is reduced.
Disclosure of Invention
The invention aims to provide a high-pressure torsion extrusion method for a fine-grain sample, which reduces the non-uniform distribution of mechanical properties and tissue states of samples prepared by traditional high-pressure torsion processing along the radial direction of the sample, realizes the consistent linear speed at each point on the surface of the sample in the torsion process, and further ensures that the prepared sample has better quality.
To achieve the above object, the solution of the present invention is:
a high-pressure torsion extrusion method for a fine-grain sample comprises the following steps:
firstly, assembling a high-pressure torsion extrusion die, wherein the die comprises an upper anvil block, a lower anvil block, a lamination sleeve and a rotation control mechanism, the lower anvil block is provided with an annular cavity, the lamination sleeve comprises a mandrel and a cylindrical part group sleeved on the mandrel, the cylindrical part group is formed by overlapping and sleeving a plurality of cylindrical parts with gradually increased radius one by one along the radial direction, the tops of the mandrel and the lamination sleeve form a circular plane, the circular plane is matched with the bottom of the annular cavity, the upper anvil block is matched with the top of the annular cavity and moves up and down along the axial direction, and a sample is placed between the upper anvil block and the lamination sleeve; the radiuses of the spindle and the driven gears of the cylindrical parts are gradually increased from inside to outside, and the heights of the driven gears are gradually increased from inside to outside, so that the bottoms of the lamination assemblies form a conical structure; the rotary control mechanism is arranged on one side of the conical structure and comprises a driving mechanism, driving gears and a transmission shaft, wherein the driving gears are sleeved on the transmission shaft from top to bottom, the number of the driving gears is equal to the sum of the number of the mandrels and the cylindrical parts, the radius of the driving gears is gradually increased from top to bottom, the driving gears and the driven gears are meshed from top to bottom, and the transmission shaft is connected with the driving mechanism;
then, after the components are assembled, placing the sample on a circular plane of the annular cavity, pressing down an upper anvil block, maintaining pressure, and starting a rotation control mechanism;
finally, the driving mechanism drives the transmission shaft to rotate, and drives the lamination suite to rotate through the engagement of the driving gear and the driven gear, wherein the engagement ratio between the driving gear and the driven gearAnd angular velocity->The relation of (2) is:
after the scheme is adopted, the gain effect of the invention is as follows:
the invention adopts a plurality of independently rotating lamination kits which are coaxially nested to replace the traditional integral lower anvil, and utilizes different meshing ratios and angular speeds between a driven gear and a driving gear on the anvilIs realized by the negative correlation ofThe anvil block rotates at a differential speed, so that the shear strain born by each area of the sample is uniform, the surface hardness, the grain refinement degree and the surface structure of the prepared sample are more uniform along the radial direction, the sample has better service performance and corrosion resistance, and a processing reinforced blank with better quality is provided for further forming a final workpiece.
Drawings
FIG. 1 is a schematic diagram of a conventional HPT mold;
FIG. 2 is a graph of center-to-center distance versus linear velocity for a conventional HPT die lower anvil;
FIG. 3 is a schematic diagram of a mold structure according to the present invention;
FIG. 4 is a schematic view of angular velocity at each location of a circular plane of the present invention;
FIG. 5 is a graph showing the relationship between the center distance L and the linear velocity V of the surface of a cylindrical sample according to the present invention;
FIG. 6 is a graph showing the relationship between the center distance L and the linear velocity V on the surface of an annular body sample according to the present invention.
Reference numerals:
the device comprises an upper anvil 1, a lower anvil 2, a lamination sleeve 3, a mandrel 4, a barrel 5, a rotation control mechanism 6, a box 7, a thrust bearing 8, a circular plane 9, a sample 10, a driven gear 11, a driving mechanism 12, a driving gear 13 and a transmission shaft 14.
Detailed Description
To obtain a diameter ofThe present invention will be described in detail below with reference to the drawings and examples.
As shown in fig. 3, the invention provides a high-pressure torsion extrusion method of a fine-grain sample, which relates to a high-pressure torsion extrusion die, the die comprises an upper anvil block 1, a lower anvil block 2, a lamination sleeve 3, a rotation control mechanism 6 and a box body 7, the lower anvil block 2 is provided with an annular cavity, the lamination sleeve 3 comprises a mandrel 4 and a cylindrical part group sleeved on the mandrel 4, the cylindrical part group is formed by overlapping and sleeving a plurality of cylindrical parts 5 with gradually increased radius along the radial direction one by one, the fit clearance of the lamination sleeve 3 is less than or equal to 0.02-0.05 mm,for the wall thickness of the tubular part 5->Is the diameter of the mandrel 4; the top of the lamination sleeve 3 forms a circular plane 9, the circular plane 9 is matched with the bottom of the annular cavity, the upper anvil 1 is matched and placed on the top of the annular cavity and moves up and down along the axial direction, the upper anvil 1 is still used for providing a lower pressure, and a sample 10 is placed between the upper anvil 1 and the lamination sleeve 3;
the bottom of the lamination suite 3 is connected with the rotation control mechanism 6, the rotation control mechanism 6 controls the lamination suite 3 to rotate and controls the angular speed of the mandrel 4 and each cylindrical part 5 to decrease from inside to outside.
The bottom of the lower anvil block 2 adopts a plurality of independently rotating cylindrical parts 5 to coaxially nest and form the discretized cylindrical lower anvil block 2, the discretization degree can be unlimited, i.e. the wall thickness of the cylindrical lower anvil block 2 can be designed according to the needs. Whereas for the discretized lower anvil 2, since the rotation control mechanism 6 is fixed thereon, in this embodiment, the rotation control mechanism 6 takes gear transmission as an example, the spindle 4 and the bottom of each cylindrical member 5 are provided with driven gears 11, the radii of the spindle 4 and the driven gears 11 of the cylindrical members 5 are gradually increased from inside to outside, and the heights of the driven gears 11 are gradually increased from inside to outside, so that the bottom of the lamination suite 3 forms a conical structure; the rotary control mechanism 6 is arranged on one side of the conical structure, the rotary control mechanism 6 comprises a driving mechanism 12, a driving gear 13 and a transmission shaft 14, the driving gear 13 is sleeved on the transmission shaft 14 from top to bottom, the driving gear 13 is connected on the transmission shaft 14 through a key, so that the driving gear 13 is ensured to synchronously and axially move in the rotating process, and specific parameters refer to national standards GB/T1096-2003, GB/T3480.1-2019 and GB/T273.2-2018. The number of the driving gears 13 is equal to the sum of the number of the mandrels 4 and the cylindrical pieces 5, the radius of each driving gear 13 is gradually increased from top to bottom, each driving gear 13 is meshed with each driven gear 11 from top to bottom, the transmission shafts 14 are connected with the driving mechanism 12, and the driving mechanism 12 drives the transmission shafts 14 to rotate. The invention utilizes the transmission shaft 14 capable of outputting torsion to drive the discretization lower anvil block 2 to rotate through a multi-stage gear, thereby providing torsion force for the round plane 9 contacted with the sample 10, and realizing different rotation angular velocities of the lamination suite 3 according to the meshing ratio, so as to control the linear velocity of each point on the surface of the sample 10 to be consistent by controlling different rotation angular velocities in the processing strengthening process of high-pressure torsion. In order to improve the structural stability, a thrust bearing 8 is arranged between the adjacent driven gears 11, and the driven gears 11 with different heights and the thrust bearings 8 are sequentially assembled on the mandrel 4 during the installation.
The lower anvil 2 is provided with a box 7 below, the box 7 wraps the bottom of the lamination suite 3 below the lower anvil 2, the thickness (diameter) of the cylindrical part 5 and the mandrel 4 should be as small as possible under the condition of ensuring the strength of the cylindrical part 5 and the mandrel 4 so as to ensure the uniformity of the performance of the obtained sample 10 along the radial direction, and the normal operation of a lubricating oil ensuring mechanism should be injected into the box 7 and the abrasion of each part should be reduced.
After the components are assembled, the upper anvil block 1 is arranged on an upper press, a sample 10 is placed on a circular plane 9 of the annular cavity, the press is pressed down and maintained, and the rotary control mechanism 6 is started; the driving mechanism 12 drives the transmission shaft 14 to rotate, and drives the lamination suite 3 to rotate through the engagement of the driving gear 13 and the driven gear 11, and the engagement ratio between the driving gear 13 and the driven gear 11 at each stageThe difference causes the angular velocity of the mandrel 4, the layers of cylinders 5 + ->In contrast, as shown in FIG. 4, the engagement ratio between the driving gear and the driven gear is +.>And angular velocity->The relation of (2) is:
in the high-pressure torsion sample process, as for a cylindrical sample, the linear velocity distribution at each point on the surface of the cylindrical sample is shown in fig. 5, compared with the traditional high-pressure torsion device, the linear velocity distribution of the cylindrical sample is nearly consistent, the cylindrical sample is in a horizontal sawtooth shape, the fluctuation amplitude of the linear velocity value of the cylindrical sample is reduced along with the increase of the number of laminated kits, but the linear velocity of the center of the sample is 0 due to the existence of a mandrel, and the linear velocity change at the surface of the sample contacted with the mandrel is obvious;
the advantages of the invention are more obvious for the annular body sample, the linear velocity distribution at each point on the surface of the annular body sample is shown in figure 6, and no region with larger change of the linear velocity exists.
The above embodiments are only preferred embodiments of the present invention, and are not limited to the present invention, and all equivalent changes made according to the design key of the present invention fall within the protection scope of the present invention.

Claims (1)

1. The high-pressure torsion extrusion method of the fine-grain sample is characterized by comprising the following steps of:
firstly, assembling a high-pressure torsion extrusion die, wherein the die comprises an upper anvil block, a lower anvil block, a lamination sleeve and a rotation control mechanism, the lower anvil block is provided with an annular cavity, the lamination sleeve comprises a mandrel and a cylindrical part group sleeved on the mandrel, the cylindrical part group is formed by overlapping and sleeving a plurality of cylindrical parts with gradually increased radius one by one along the radial direction, the tops of the mandrel and the lamination sleeve form a circular plane, the circular plane is matched with the bottom of the annular cavity, and the upper anvil block is matched with the top of the annular cavity and moves up and down along the axial direction, so that a sample is placed between the upper anvil block and the lamination sleeve; the radiuses of the spindle and the driven gears of the cylindrical parts are gradually increased from inside to outside, and the heights of the driven gears are gradually increased from inside to outside, so that the bottoms of the lamination assemblies form a conical structure; the rotary control mechanism is arranged on one side of the conical structure and comprises a driving mechanism, driving gears and a transmission shaft, wherein the driving gears are sleeved on the transmission shaft from top to bottom, the driving gears are connected to the transmission shaft through keys so as to ensure that the driving gears synchronously and axially do not move in the rotating process, the number of the driving gears is equal to the sum of the number of the mandrels and the cylindrical parts, the radius of the driving gears gradually increases from top to bottom, the driving gears and the driven gears are meshed from top to bottom, and the transmission shaft is connected with the driving mechanism;
then, after the components are assembled, placing the sample on a circular plane of the annular cavity, pressing down an upper anvil block, maintaining pressure, and starting a rotation control mechanism;
finally, the driving mechanism drives the transmission shaft to rotate, and drives the lamination suite to rotate through the engagement of the driving gear and the driven gear, and the engagement ratio between the driving gear and the driven gear of each stage is from bottom to topAngular velocity from the inside to the outside spindle and the barrel>The relation of (2) is:
due to the engagement ratio between the driving gear and the driven gear of each stageDifferent angular velocities of the mandrel and the cylindrical parts of the layers>In the process of processing and strengthening the high-pressure torsion, the linear velocity of each point on the surface of the sample from inside to outside is controlled to be consistent by controlling the different rotation angular velocities of the lamination sleeve and the mandrel.
CN202111149561.4A 2021-09-29 2021-09-29 High-pressure torsion extrusion method for fine-grain sample Active CN113804559B (en)

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