WO2018174405A1 - Torsional severe plastic deformation method for metal bar, employing surface polishing to improve mechanical properties of metal bar - Google Patents

Torsional severe plastic deformation method for metal bar, employing surface polishing to improve mechanical properties of metal bar Download PDF

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Publication number
WO2018174405A1
WO2018174405A1 PCT/KR2018/001541 KR2018001541W WO2018174405A1 WO 2018174405 A1 WO2018174405 A1 WO 2018174405A1 KR 2018001541 W KR2018001541 W KR 2018001541W WO 2018174405 A1 WO2018174405 A1 WO 2018174405A1
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Prior art keywords
metal bar
torsional
present
metal
torsion
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PCT/KR2018/001541
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French (fr)
Korean (ko)
Inventor
김형섭
문지현
엄호용
윤재익
백승미
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포항공과대학교 산학협력단
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Priority to US16/495,394 priority Critical patent/US20200009631A1/en
Publication of WO2018174405A1 publication Critical patent/WO2018174405A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D11/00—Bending not restricted to forms of material mentioned in only one of groups B21D5/00, B21D7/00, B21D9/00; Bending not provided for in groups B21D5/00 - B21D9/00; Twisting
    • B21D11/14—Twisting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D11/00—Bending not restricted to forms of material mentioned in only one of groups B21D5/00, B21D7/00, B21D9/00; Bending not provided for in groups B21D5/00 - B21D9/00; Twisting
    • B21D11/22—Auxiliary equipment, e.g. positioning devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D43/00—Feeding, positioning or storing devices combined with, or arranged in, or specially adapted for use in connection with, apparatus for working or processing sheet metal, metal tubes or metal profiles; Associations therewith of cutting devices
    • B21D43/006—Feeding elongated articles, such as tubes, bars, or profiles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
    • B21J1/02—Preliminary treatment of metal stock without particular shaping, e.g. salvaging segregated zones, forging or pressing in the rough
    • B21J1/025—Preliminary treatment of metal stock without particular shaping, e.g. salvaging segregated zones, forging or pressing in the rough affecting grain orientation
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
    • C21D7/10—Modifying the physical properties of iron or steel by deformation by cold working of the whole cross-section, e.g. of concrete reinforcing bars
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B27/00—Other grinding machines or devices
    • B24B27/033—Other grinding machines or devices for grinding a surface for cleaning purposes, e.g. for descaling or for grinding off flaws in the surface
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B5/00—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor
    • B24B5/18—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centreless means for supporting, guiding, floating or rotating work
    • B24B5/22—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centreless means for supporting, guiding, floating or rotating work for grinding cylindrical surfaces, e.g. on bolts
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2261/00—Machining or cutting being involved

Definitions

  • the present invention applies surface polishing to a method of applying torsional rigidity to a conventional metal rod, and more specifically, forms a gradient structure through shear deformation formed by applying a huge shear stress through torsion while substantially maintaining a shape. It relates to a torsional rigid plastic processing method of metal rods that can improve the mechanical properties of the material by ultra-fine or nano-crystallized microstructure of the tube material.
  • ultrafine / nano grains is important not only for the amount of plastic strain applied to the material, such as compression, tensile, and shear deformation, but also for the shape of the material before and after the process to allow a repeating process to apply a large amount of plastic strain. It is important to design the mold substantially the same.
  • ECAP Equal Channel Angular Pressing
  • HPT High-Pressure Torsion
  • ARB Accumulative Roll Bonding
  • ECAR Equal Channel Angular Rolling
  • the ultrafine / nanocrystalline material when the ultrafine / nanocrystalline material is formed, the strength and hardness are improved while the ductility decreases.
  • Gradient structure of grain size has been suggested as a solution to solve this phenomenon.
  • the metal material has a gradient structure in grain size, the ductility increases due to the region composed of large grains, and the strength and hardness are improved by the region composed of ultrafine / nano grains, so that the opposite mechanical properties are compatible. . Therefore, the gradient structure has emerged as a solution to the ductility reduction problem in ultrafine / nanocrystalline metal materials.
  • Gradient structure can be formed through high-pressure torsion (HPT) of the existing rigid plastic processing method, which has a disadvantage in that the size of the produced material is limited because it requires high pressure. Therefore, a simple torsion process is required as a processing method for producing a bulk material having a gradient structure.
  • HPT high-pressure torsion
  • the problem to be solved by the present invention is to add a surface polishing process to the process of adding torsional rigidity to the existing metal bar, it is possible to perform large deformation processing compared to the conventional torsion processing and to make microstructure or ultra-crystallization microstructure It is to provide a torsionally rigid processing method of metal rods that can form a grain size gradient structure to improve the mechanical properties of the metal rods.
  • a torsionally rigid processing method of metal rods which is carried out in an intermittent manner in which the process is temporarily stopped and carried out, which increases the amount of torsional rotation or shear strain applied to the metal rods.
  • the torsional rigid plastic processing method of the present invention it is possible to form a gradient structure having a grain size by applying shear deformation to the material while maintaining the shape of the metal rod, and ultrafine crystallization of the microstructure, thereby improving the mechanical properties of the material. .
  • the torsional rigidity processing method of the present invention can improve the degree of gradient and the degree of microcrystallization of the microstructure by applying a larger amount of deformation than the conventional torsional deformation through surface polishing.
  • the torsional rigidity processing method of the present invention is capable of controlling the torsional deformation and the mechanical properties by adjusting the rotational speed.
  • the torsionally rigid processing method of the present invention by controlling the number of revolutions of the mold can be freely adjusted the amount of deformation applied to the material is easy to reinforce the physical properties of the metal bar and to control the microstructure.
  • FIG. 1 is a view showing a torsional rigid plastic working method and processing equipment according to an embodiment of the present invention.
  • FIG. 2 is a view showing a cross section of the specimen used in the embodiment of the present invention.
  • FIG 3 is a view showing each metal rod before and after the torsional rigid plastic working process according to an embodiment of the present invention.
  • Figure 4 is a result of comparing the hardness of the metal bar according to an embodiment of the present invention with the conventional metal bar.
  • FIG. 5 is a schematic diagram showing a region subjected to the analysis in the metal rods processed according to the embodiment of the present invention.
  • FIG. 6 shows the results of backscattered electron diffraction (EBSD) analysis of metal rods subjected to simple torsion processing.
  • EBSD backscattered electron diffraction
  • EBSD backscattered electron diffraction
  • FIG. 1 is a view showing a torsional rigid plastic working method and processing equipment according to an embodiment of the present invention.
  • FIG. 2 is a view showing a cross section of the specimen used in the embodiment of the present invention.
  • the torsional rigid plastic working method of the metal bar is a surface defect generated on the surface of the metal bar by the step of applying a torsion to the metal bar, and the step of applying the torsion Including a step of removing, the step of removing the surface defects, the continuous method or the intermittent method to temporarily stop and perform the torsional process, which is made in conjunction with the torsional process, and added to the metal rod Losing can increase the amount of torsional rotation or shear strain.
  • the twisting process may include installing a metal rod between the pair of molds and rotating at least one of the pair of molds to perform the twisting of the metal rod.
  • metal molds are fitted on both sides of upper and lower parts of metal bars, and surface polishing is performed while applying twist to the metal bars, thereby making the microstructure of the metal bars ultrafine or nanocrystalline. Gradient structures of size can be formed.
  • a gradient structure having a grain size may be formed in the metal bar by using the shear deformation formed by the shear stress.
  • the process of removing the surface defects may include a polishing process.
  • the polishing process may be performed by using a silicon carbide (SiC) abrasive paper as the surface polishing process, or by using an abrasive material whose surface roughness decreases as the amount of torsional rotation or shear strain increases.
  • SiC silicon carbide
  • the surface polishing step after removing the metal bar from the mold, the surface of the metal bar is intermittently polished, or the surface of the metal bar fixed by the mold can be continuously polished.
  • silicon carbide (SiC) abrasive paper having sizes of x400, x600, x800, and x1200 may be used.
  • the surface roughness of each silicon carbide abrasive paper is 22 ⁇ ⁇ , 15 ⁇ ⁇ , 10 ⁇ ⁇ , and 5 ⁇ ⁇ , whereby the surface roughness of the specimen (metal rod) is formed below the corresponding roughness when surface polishing is performed with the silicon carbide abrasive paper.
  • the roughness of the surface formed during the twisting process per one time may be polished to about 5 ⁇ m or less.
  • the surface defects formed by the torsion in the surface polishing process are not polished to about 5 ⁇ m or less, and then proceeds to the next step, shear failure may proceed from the remaining defects and the torsion process may be stopped. In addition, even if the surface defects have been removed, if the surface polishing is excessively progressed may cause a problem that the cross-sectional area of the specimen is reduced more than necessary.
  • the maximum torsional rotation amount or the maximum shear strain at which deformation is stopped due to shear failure may occur depending on the material properties.
  • x400, x600, x800, x1200 silicon carbide (SiC) abrasive paper during the process of applying the twist to increase the maximum amount of torsional rotation or maximum shear strain of each material by delaying the shear failure through surface polishing.
  • Surface polishing can be performed in order.
  • the closer to the maximum amount of torsional rotation or maximum shear strain of the metal bar increases the frequency or frequency of surface polishing to remove surface defects at the point where stress (stress) is concentrated, thereby increasing the maximum amount of torsional rotation or maximum shear strain. The efficiency can be maximized.
  • Torsional rigid plastic processing method of the present invention increases the maximum amount of torsional rotation or the maximum shear strain compared to the conventional metal bar to apply more plastic deformation to form an ultrafine grain or nano-crystallization and grain size gradient structure of the metal bar It is easy to strengthen the physical properties and control the microstructure.
  • the torsional rigidity processing method of the present invention can improve the strength and hardness by applying more shear plastic deformation than the conventional simple torsion process through surface polishing.
  • FIG. 3 is a view showing each metal rod before and after the process of applying the torsion according to an embodiment of the present invention.
  • Figure 4 is a result of comparing the hardness of the metal bar according to an embodiment of the present invention with the conventional metal bar. Referring to FIG. 4, it can be seen that the metal rod according to the embodiment of the present invention has more deformation and improved hardness by surface polishing.
  • FIG. 5 is a schematic diagram showing a region subjected to the analysis in the metal rods processed according to the embodiment of the present invention.
  • FIG. 6 shows the results of backscattered electron diffraction (EBSD) analysis of metal rods subjected to simple torsion processing.
  • EBSD backscattered electron diffraction
  • FIG. 7 is a result of backscattered electron diffraction (EBSD) analysis of a metal rod according to an embodiment of the present invention. Here, the analysis was performed based on the position of FIG. 5.
  • EBSD backscattered electron diffraction
  • FIG. 8 is a table comparing the embodiment of the present invention with a simple torsion processing for the metal bar. Referring to Figure 8, it can be seen the degree of ultra-fine grain or nano-crystallization of the metal bar according to an embodiment of the present invention.
  • the torsional rigid plastic processing method of the present invention it is possible to form a gradient structure having a grain size by applying shear deformation to the material while maintaining the shape of the metal rod, and ultrafine crystallization of the microstructure, thereby improving the mechanical properties of the material. .
  • the torsional rigidity processing method of the present invention can improve the degree of gradient and the degree of microcrystallization of the microstructure by applying a larger amount of deformation than the conventional torsional deformation through surface polishing.
  • the torsional rigidity processing method of the present invention is capable of controlling the torsional deformation and the mechanical properties by adjusting the rotational speed.
  • the torsionally rigid processing method of the present invention by controlling the number of revolutions of the mold can be freely adjusted the amount of deformation applied to the material is easy to reinforce the physical properties of the metal bar and to control the microstructure.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
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  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
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Abstract

The present invention relates to a torsional severe plastic deformation method for a metal bar, to which surface polishing is applied to improve the mechanical properties of the metal bar. Provided according to an embodiment of the present invention is a torsional severe plastic deformation method for a metal bar, comprising the steps of: applying torsion to a metal bar; and removing surface defects on the surface of the metal bar, which are caused by the torsion application step, wherein the surface defect removal step is carried out by a continuous method in which the surface defect removal step is performed together with the torsion application step or by a discontinuous method in which the torsion application step is paused and then the surface defect removal step is performed, and the surface defect removal step increases the amount of torsional rotation or the shear strain applied to the metal bar.

Description

표면연마를 적용시켜 기계적 성질이 향상된 금속 봉재의 비틀림 강소성 가공법Torsional Rigidity Machining of Metal Bars with Improved Mechanical Properties by Applying Surface Polishing
본 발명은 기존의 금속 봉재에 비틀림 강소성을 가하는 방법에 표면 연마를 적용한 것으로서, 보다 구체적으로는 형상을 실질적으로 유지하면서 비틀림을 통한 거대한 전단 응력을 가하여 형성되는 전단 변형을 통해 구배 구조를 형성하며 금속관재의 미세조직을 초미세결정립화 또는 나노결정립화시켜 소재의 기계적 성질을 향상시킬 수 있는 금속 봉재의 비틀림 강소성 가공법에 관한 것이다. The present invention applies surface polishing to a method of applying torsional rigidity to a conventional metal rod, and more specifically, forms a gradient structure through shear deformation formed by applying a huge shear stress through torsion while substantially maintaining a shape. It relates to a torsional rigid plastic processing method of metal rods that can improve the mechanical properties of the material by ultra-fine or nano-crystallized microstructure of the tube material.
금속재료에 소성 변형이 가해지면 소경계각 전위셀 구조가 형성되고 소성 변형량이 증가할수록 전위셀 아결정립의 결정립계각 증가와 더불어 결정립이 점차 미세화되는 현상이 발생한다. 이를 이용하여 소재에 큰 소성 변형을 가해주어 결정립을 초미세결정립화 또는 나노결정립화하게 되면 변형 전의 금속소재와 비교하여 그 기계적 성질(강도, 경도, 내연마성 및 초소성 등)이 매우 향상되므로, 종래의 형상 성형을 위주로 한 소재 가공법에서 벗어나 새로운 초미세/나노결정소재를 제조하기 위한 가공법으로서 그 중요성과 필요성이 점차 커지고 있다.When plastic deformation is applied to the metal material, a small boundary angle dislocation cell structure is formed, and as the amount of plastic deformation increases, the grain boundary of the dislocation cell sub-crystal grains increases and the grains gradually become finer. By applying a large plastic deformation to the material by using this, if the crystal grains are ultrafine or nanocrystalline, the mechanical properties (strength, hardness, abrasion resistance and superplasticity, etc.) are greatly improved compared to the metal material before deformation, Its importance and necessity are gradually increasing as a processing method for manufacturing a new ultra fine / nanocrystalline material away from the conventional material processing method mainly for shape molding.
이러한 초미세/나노결정립 형성에는 압축, 인장, 전단 변형과 같은, 소재에 가해지는 소성변형량이 중요할 뿐 아니라, 많은 양의 소성변형량을 가할 수 있는 반복공정이 가능하도록 공정 전후의 소재의 형상이 실질적으로 동일하게 금형을 설계하는 것이 중요하다.The formation of ultrafine / nano grains is important not only for the amount of plastic strain applied to the material, such as compression, tensile, and shear deformation, but also for the shape of the material before and after the process to allow a repeating process to apply a large amount of plastic strain. It is important to design the mold substantially the same.
이러한 조건을 만족하는 강소성 가공법으로는 현재까지, 등통로각압축 공정(ECAP: Equal Channel Angular Pressing), 고압비틀림 공정(HPT: High-Pressure torsion), 반복접착압연 공정(ARB: Accumulative Roll Bonding), 등통로각압연 공정(ECAR: Equal Channel Angular Rolling) 등이 개발되어 있다.Rigid plastic processing that satisfies these conditions is, to date, Equal Channel Angular Pressing (ECAP), High-Pressure Torsion (HPT), Accumulative Roll Bonding (ARB), Equal Channel Angular Rolling (ECAR) has been developed.
하지만 초미세/나노결정소재가 형성될 경우 강도, 경도가 향상되는 반면 연성이 감소하는 현상이 발생한다. 이러한 연성이 감소하는 현상을 해결하기 위한 해결책으로 결정립 크기의 구배 구조가 제시되고 있다. 금속소재가 결정립 크기에 있어서 구배 구조를 가질 경우, 큰 결정립으로 이루어진 영역에 의해 연성이 증가하고 초미세/나노결정립으로 이루어진 영역에 의해 강도, 경도가 향상되어 상반되는 기계적 성질들이 양립할 수 있게 된다. 따라서 초미세/나노결정립화된 금속소재에 있어서 구배 구조는 연성 감소 문제의 해결책으로 대두되고 있다.However, when the ultrafine / nanocrystalline material is formed, the strength and hardness are improved while the ductility decreases. Gradient structure of grain size has been suggested as a solution to solve this phenomenon. When the metal material has a gradient structure in grain size, the ductility increases due to the region composed of large grains, and the strength and hardness are improved by the region composed of ultrafine / nano grains, so that the opposite mechanical properties are compatible. . Therefore, the gradient structure has emerged as a solution to the ductility reduction problem in ultrafine / nanocrystalline metal materials.
기존 강소성 가공법 중 고압비틀림 공정(HPT: High-Pressure torsion)을 통해 구배 구조를 형성할 수 있는데, 이 가공법의 경우 높은 압력을 필요로 하기 때문에 생산되는 재료의 크기가 제한된다는 단점이 있다. 따라서 구배 구조를 가지는 벌크 재료를 생산하는 가공법으로써 단순 비틀림 공정이 요구되고 있다.Gradient structure can be formed through high-pressure torsion (HPT) of the existing rigid plastic processing method, which has a disadvantage in that the size of the produced material is limited because it requires high pressure. Therefore, a simple torsion process is required as a processing method for producing a bulk material having a gradient structure.
이러한 비틀림 강소성 공정의 경우 전단 파괴현상에 의해 중단 되는데 충분한 소성 변형이 가해지지 않은 채 중단되는 경우가 있어 전단 파괴현상을 지연시키는 기법이 요구되고 있다. 비틀림 가공법의 경우 중심축으로부터 거리가 멀어질수록 많은 양의 변형이 가해지는 특징을 가지고 있다. 따라서 가장 많은 양의 변형이 가해지는 표면에서 결함이 생성되고 공정이 진행되면서 결함이 생긴 지점에서 전단 파괴현상이 진행된다.In this torsional rigid plastic process, it is interrupted without sufficient plastic deformation in order to be interrupted by shear failure, and thus a technique for delaying shear failure is required. In the case of torsion processing, the greater the distance from the central axis, the greater the amount of deformation. Therefore, defects are generated on the surface where the most amount of deformation is applied, and shear failure occurs at the point where the defects occur as the process proceeds.
본 발명이 해결하고자 하는 과제는 기존의 금속 봉재에 비틀림 강소성을 가하는 과정에 표면 연마 공정을 추가하여 기존 비틀림 가공에 비해 대변형 가공이 가능하고 미세 조직을 초미세결정립화 또는 나노결정립화 시킬 수 있으며 결정립 크기의 구배 구조를 형성하여 금속 봉재의 기계적 성질을 향상시킬 수 있는 금속 봉재의 비틀림 강소성 가공법을 제공하는 것이다.The problem to be solved by the present invention is to add a surface polishing process to the process of adding torsional rigidity to the existing metal bar, it is possible to perform large deformation processing compared to the conventional torsion processing and to make microstructure or ultra-crystallization microstructure It is to provide a torsionally rigid processing method of metal rods that can form a grain size gradient structure to improve the mechanical properties of the metal rods.
본 발명의 일 실시예에 따르면, 금속 봉재에 비틀림을 가하는 공정; 및 상기 비틀림을 가하는 공정에 의해 상기 금속 봉재의 표면에 생성되는 표면 결함을 제거하는 공정을 포함하되, 상기 표면 결함을 제거하는 공정은, 상기 비틀림을 가하는 공정과 함께 이루어지는 연속 방식 또는 상기 비틀림을 가하는 공정을 일시적으로 중단하고 실시하는 단속 방식으로 수행하며, 상기 금속 봉재에 가해지는 비틀림 회전량 또는 전단 변형률을 증가시키는, 금속 봉재의 비틀림 강소성 가공법을 제공한다.According to one embodiment of the invention, the step of applying a torsion to the metal rod; And removing a surface defect generated on the surface of the metal rod by the twisting step, wherein the removing of the surface defect includes a continuous method or the twisting step that is performed together with the twisting step. Provided is a torsionally rigid processing method of metal rods, which is carried out in an intermittent manner in which the process is temporarily stopped and carried out, which increases the amount of torsional rotation or shear strain applied to the metal rods.
본 발명의 비틀림 강소성 가공법에 의하면, 금속 봉재 형상을 유지하며 재료에 전단 변형을 가하여 결정립 크기의 구배 구조를 형성시킬 수 있고 미세조직의 초미세결정립화가 가능하여, 재료의 기계적 물성을 향상시킬 수 있다. According to the torsional rigid plastic processing method of the present invention, it is possible to form a gradient structure having a grain size by applying shear deformation to the material while maintaining the shape of the metal rod, and ultrafine crystallization of the microstructure, thereby improving the mechanical properties of the material. .
또한, 본 발명의 비틀림 강소성 가공법은 표면 연마를 통해 기존 비틀림 변형보다 더 많은 양의 변형을 가하여 구배 정도 및 미세조직의 미세결정립화 정도를 향상시킬 수 있다.In addition, the torsional rigidity processing method of the present invention can improve the degree of gradient and the degree of microcrystallization of the microstructure by applying a larger amount of deformation than the conventional torsional deformation through surface polishing.
또한, 본 발명의 비틀림 강소성 가공법은 회전 속도를 조절하여 비틀림 변형의 조절 및 기계적 성질의 조절이 가능하다. In addition, the torsional rigidity processing method of the present invention is capable of controlling the torsional deformation and the mechanical properties by adjusting the rotational speed.
또한, 본 발명의 비틀림 강소성 가공법은, 금형의 회전수를 조절하여 재료에 가해지는 변형량을 자유자재로 조절할 수 있어 금속 봉재의 물성 강화 및 미세조직 조절에 용이하다.In addition, the torsionally rigid processing method of the present invention, by controlling the number of revolutions of the mold can be freely adjusted the amount of deformation applied to the material is easy to reinforce the physical properties of the metal bar and to control the microstructure.
도 1은 본 발명의 실시예에 따른 비틀림 강소성 가공법과 가공 장비를 나타내는 도면이다.1 is a view showing a torsional rigid plastic working method and processing equipment according to an embodiment of the present invention.
도 2는 본 발명의 실시예에서 사용한 시편의 단면을 나타내는 도면이다.2 is a view showing a cross section of the specimen used in the embodiment of the present invention.
도 3은 본 발명의 실시예에 따른 비틀림 강소성 가공 공정 전후 각각의 금속 봉재를 나타내는 도면이다.3 is a view showing each metal rod before and after the torsional rigid plastic working process according to an embodiment of the present invention.
도 4는 본 발명의 실시예에 따른 금속 봉재의 경도를 기존 금속 봉재와 비교한 결과이다.Figure 4 is a result of comparing the hardness of the metal bar according to an embodiment of the present invention with the conventional metal bar.
도 5는 본 발명의 실시예에 따라 가공한 금속 봉재에서 분석을 실시한 영역을 나타낸 모식도이다.5 is a schematic diagram showing a region subjected to the analysis in the metal rods processed according to the embodiment of the present invention.
도 6은 단순 비틀림 가공을 마친 금속봉재의 후방산란전자회절(EBSD) 분석 결과이다.FIG. 6 shows the results of backscattered electron diffraction (EBSD) analysis of metal rods subjected to simple torsion processing. FIG.
도 7은 본 발명의 실시예에 따른 금속봉재의 후방산란전자회절(EBSD) 분석 결과이다.7 is a result of backscattered electron diffraction (EBSD) analysis of a metal rod according to an embodiment of the present invention.
도 8은 금속 봉재에 대한 단순 비틀림 가공과 본 발명의 실시예를 비교한 표이다.8 is a table comparing the embodiment of the present invention with a simple torsion processing for the metal bar.
이하에서는, 본 발명의 바람직한 실시예에 기초하여 본 발명을 보다 구체적으로 설명한다. 그러나, 하기 실시예는 본 발명의 이해를 돕기 위한 일 예에 불과한 것으로 이에 의해 본 발명의 권리범위가 축소되거나 한정되는 것은 아니다.Hereinafter, the present invention will be described in more detail based on the preferred embodiments of the present invention. However, the following examples are merely examples to help the understanding of the present invention, whereby the scope of the present invention is not reduced or limited.
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본 발명에서는 기존 비틀림 공정에 표면의 결함을 연속적으로 제거하는 공정을 추가하여 전단 파괴현상을 지연시켜 재료에 충분한 소성 변형량을 가하여 초미세결정립 또는 나노결정립 형성 과정을 개선하도록 제안되었다.In the present invention, it is proposed to add a process of continuously removing defects of the surface to the existing torsion process to delay shear failure and to add a sufficient amount of plastic deformation to the material to improve the ultrafine or nanocrystalline formation process.
본 발명의 표면 처리를 적용할 경우 기존의 비틀림 강소성 가공법에 비해 표면 파괴를 지연시킴으로써 더욱 커다란 변형을 부과시키고 더욱 미세한 초미세결정립화 또는 나노경정립화 정도를 강화할 수 있다.In the case of applying the surface treatment of the present invention, it is possible to impose more deformation and reinforce the degree of finer microcrystallization or nanohardening by retarding the surface fracture as compared with the conventional torsional rigid plastic processing method.
도 1은 본 발명의 실시예에 따른 비틀림 강소성 가공법과 가공 장비를 나타내는 도면이다.1 is a view showing a torsional rigid plastic working method and processing equipment according to an embodiment of the present invention.
도 2는 본 발명의 실시예에서 사용한 시편의 단면을 나타내는 도면이다.2 is a view showing a cross section of the specimen used in the embodiment of the present invention.
도 1 및 도 2를 참조하면, 본 발명의 실시예에 따른 금속 봉재의 비틀림 강소성 가공법은 금속 봉재에 비틀림을 가하는 공정, 및 상기 비틀림을 가하는 공정에 의해 상기 금속 봉재의 표면에 생성되는 표면 결함을 제거하는 공정을 포함하되, 상기 표면 결함을 제거하는 공정은, 상기 비틀림을 가하는 공정과 함께 이루어지는 연속 방식 또는 상기 비틀림을 가하는 공정을 일시적으로 중단하고 실시하는 단속 방식으로 수행하며, 상기 금속 봉재에 가해지는 비틀림 회전량 또는 전단 변형률을 증가시킬 수 있다.1 and 2, the torsional rigid plastic working method of the metal bar according to an embodiment of the present invention is a surface defect generated on the surface of the metal bar by the step of applying a torsion to the metal bar, and the step of applying the torsion Including a step of removing, the step of removing the surface defects, the continuous method or the intermittent method to temporarily stop and perform the torsional process, which is made in conjunction with the torsional process, and added to the metal rod Losing can increase the amount of torsional rotation or shear strain.
구체적으로, 비틀림을 가하는 공정은 한쌍의 금형 사이에 금속 봉재를 설치하는 단계 및 한쌍의 금형 중 적어도 하나를 회전시켜 금속 봉재의 비틀림을 실행하는 단계를 포함할 수 있다.Specifically, the twisting process may include installing a metal rod between the pair of molds and rotating at least one of the pair of molds to perform the twisting of the metal rod.
예를 들면, 금속 봉재의 상하부 양측에 금속 봉재의 형상에 맞춘 금형을 장착하고, 금속 봉재에 비틀림을 가하면서 표면 연마 작업을 실행하여 금속 봉재의 미세조직을 초미세결정립화 또는 나노결정립화 시키며 결정립 크기의 구배 구조를 형성할 수 있다.For example, metal molds are fitted on both sides of upper and lower parts of metal bars, and surface polishing is performed while applying twist to the metal bars, thereby making the microstructure of the metal bars ultrafine or nanocrystalline. Gradient structures of size can be formed.
여기서, 금속 봉재의 비틀림을 실행하는 단계에서는 전단 응력에 의해 형성되는 전단 변형을 이용하여 금속 봉재에서 결정립 크기의 구배 구조를 형성할 수 있다.Here, in the torsion of the metal bar, a gradient structure having a grain size may be formed in the metal bar by using the shear deformation formed by the shear stress.
표면 결함을 제거하는 공정은 연마 공정을 포함할 수 있다.The process of removing the surface defects may include a polishing process.
여기서, 연마 공정은 표면 연마 공정으로서, 탄화규소(SiC) 연마지를 사용하거나, 비틀림 회전량 또는 전단 변형률이 증가할수록 표면 거칠기가 감소하는 연마재를 사용하여 수행할 수 있다.Here, the polishing process may be performed by using a silicon carbide (SiC) abrasive paper as the surface polishing process, or by using an abrasive material whose surface roughness decreases as the amount of torsional rotation or shear strain increases.
또한, 표면 연마 공정에서는 금형으로부터 금속 봉재를 분리한 후 금속 봉재의 표면을 단속적으로 연마하거나, 금형에 의해 고정된 금속 봉재의 표면을 연속적으로 연마할 수 있다.In addition, in the surface polishing step, after removing the metal bar from the mold, the surface of the metal bar is intermittently polished, or the surface of the metal bar fixed by the mold can be continuously polished.
이때, 표면 연마 공정에서는 x400, x600, x800, x1200 크기의 탄화규소(SiC) 연마지(paper)를 사용할 수 있다. 각각의 탄화규소 연마지의 표면 거칠기는 22㎛, 15㎛, 10㎛, 5㎛로 특정 탄화규소 연마지로 표면 연마를 진행하였을 때 해당 거칠기 이하로 시편(금속 봉재) 표면의 거칠기가 형성되게 된다.In this case, in the surface polishing process, silicon carbide (SiC) abrasive paper having sizes of x400, x600, x800, and x1200 may be used. The surface roughness of each silicon carbide abrasive paper is 22 占 퐉, 15 占 퐉, 10 占 퐉, and 5 占 퐉, whereby the surface roughness of the specimen (metal rod) is formed below the corresponding roughness when surface polishing is performed with the silicon carbide abrasive paper.
또한, 표면 연마 공정을 단속적으로 수행할 경우 1회당 비틀림 공정 과정 중에 형성된 표면의 거칠기를 약 5㎛ 이하로 연마할 수 있다.In addition, when the surface polishing process is performed intermittently, the roughness of the surface formed during the twisting process per one time may be polished to about 5 μm or less.
만약, 표면 연마 공정에서 비틀림에 의해 형성된 표면의 결함을 약 5㎛ 이하로 연마하지 않고 다음 단계로 넘어갈 경우, 남아있는 결함에서 전단 파괴현상이 진행되어 비틀림 공정이 중단되는 문제점이 발생할 수 있다. 또한, 표면의 결함이 제거되었음에도 불구하고 지나치게 표면 연마를 진행할 경우 필요 이상으로 시편의 단면적이 감소하는 문제점이 발생할 수 있다.If the surface defects formed by the torsion in the surface polishing process are not polished to about 5 μm or less, and then proceeds to the next step, shear failure may proceed from the remaining defects and the torsion process may be stopped. In addition, even if the surface defects have been removed, if the surface polishing is excessively progressed may cause a problem that the cross-sectional area of the specimen is reduced more than necessary.
일정 회전 속도로 비틀림 공정을 진행하였을 때, 재료 본연의 물성에 따라 전단 파괴현상이 발생하여 변형이 중단되는 최대 비틀림 회전량 또는 최대 전단 변형률이 다를 수 있다.When the torsion process is performed at a constant rotational speed, the maximum torsional rotation amount or the maximum shear strain at which deformation is stopped due to shear failure may occur depending on the material properties.
본 발명에서는 표면 연마를 통해 전단파괴 현상을 지연시켜 각 재료의 최대 비틀림 회전량 또는 최대 전단 변형률을 증가시키기 위해 비틀림을 가하는 공정 중에 x400, x600, x800, x1200 탄화규소(SiC) 연마지(paper) 순서로 표면 연마 작업을 실시할 수 있다. 이때, 금속 봉재의 최대 비틀림 회전량 또는 최대 전단 변형률에 가까워질수록 표면 연마 작업 빈도 또는 횟수를 늘려 스트레스(응력)가 집중되는 지점의 표면 결함을 제거함으로써 최대 비틀림 회전량 또는 최대 전단 변형률이 증가되는 효율을 극대화할 수 있다.In the present invention, x400, x600, x800, x1200 silicon carbide (SiC) abrasive paper during the process of applying the twist to increase the maximum amount of torsional rotation or maximum shear strain of each material by delaying the shear failure through surface polishing. Surface polishing can be performed in order. At this time, the closer to the maximum amount of torsional rotation or maximum shear strain of the metal bar increases the frequency or frequency of surface polishing to remove surface defects at the point where stress (stress) is concentrated, thereby increasing the maximum amount of torsional rotation or maximum shear strain. The efficiency can be maximized.
본 발명의 비틀림 강소성 가공법은 기존 금속 봉재에 비해 최대 비틀림 회전량 또는 최대 전단 변형률을 증가시켜 더 많은 소성 변형을 가해 향상된 초미세결정립화 또는 나노결정립화와, 결정립 크기의 구배 구조를 형성하여 금속 봉재의 물성 강화 및 미세조직 조절에 용이하다. 또한, 본 발명의 비틀림 강소성 가공법은 표면 연마를 통해 기존의 단순 비틀림 공정에 비해 더 많은 전단 소성 변형을 가하여 강도 및 경도를 향상시킬 수 있다.Torsional rigid plastic processing method of the present invention increases the maximum amount of torsional rotation or the maximum shear strain compared to the conventional metal bar to apply more plastic deformation to form an ultrafine grain or nano-crystallization and grain size gradient structure of the metal bar It is easy to strengthen the physical properties and control the microstructure. In addition, the torsional rigidity processing method of the present invention can improve the strength and hardness by applying more shear plastic deformation than the conventional simple torsion process through surface polishing.
도 3은 본 발명의 실시예에 따른 비틀림을 가하는 공정 전후 각각의 금속 봉재를 나타내는 도면이다.3 is a view showing each metal rod before and after the process of applying the torsion according to an embodiment of the present invention.
도 4는 본 발명의 실시예에 따른 금속 봉재의 경도를 기존 금속 봉재와 비교한 결과이다. 도 4를 참조하면, 본 발명의 실시예에 따른 금속 봉재는 표면 연마에 의해 더 많은 변형량이 가해진 것과 향상된 경도를 갖는 것을 확인할 수 있다.Figure 4 is a result of comparing the hardness of the metal bar according to an embodiment of the present invention with the conventional metal bar. Referring to FIG. 4, it can be seen that the metal rod according to the embodiment of the present invention has more deformation and improved hardness by surface polishing.
도 5는 본 발명의 실시예에 따라 가공한 금속 봉재에서 분석을 실시한 영역을 나타낸 모식도이다.5 is a schematic diagram showing a region subjected to the analysis in the metal rods processed according to the embodiment of the present invention.
도 6은 단순 비틀림 가공을 마친 금속봉재의 후방산란전자회절(EBSD) 분석 결과이다. 여기서는, 도 5의 위치를 기반으로 분석을 진행하였다. FIG. 6 shows the results of backscattered electron diffraction (EBSD) analysis of metal rods subjected to simple torsion processing. FIG. Here, the analysis was performed based on the position of FIG. 5.
도 7은 본 발명의 실시예에 따른 금속봉재의 후방산란전자회절(EBSD) 분석 결과이다. 여기서는, 도 5의 위치를 기반으로 분석을 진행하였다.7 is a result of backscattered electron diffraction (EBSD) analysis of a metal rod according to an embodiment of the present invention. Here, the analysis was performed based on the position of FIG. 5.
도 8은 금속 봉재에 대한 단순 비틀림 가공과 본 발명의 실시예를 비교한 표이다. 도 8을 참조하면, 본 발명의 실시예에 따른 금속 봉재의 초미세결정립화 또는 나노결정립화의 정도를 확인 할 수 있다.8 is a table comparing the embodiment of the present invention with a simple torsion processing for the metal bar. Referring to Figure 8, it can be seen the degree of ultra-fine grain or nano-crystallization of the metal bar according to an embodiment of the present invention.
본 발명의 비틀림 강소성 가공법에 의하면, 금속 봉재 형상을 유지하며 재료에 전단 변형을 가하여 결정립 크기의 구배 구조를 형성시킬 수 있고 미세조직의 초미세결정립화가 가능하여, 재료의 기계적 물성을 향상시킬 수 있다. According to the torsional rigid plastic processing method of the present invention, it is possible to form a gradient structure having a grain size by applying shear deformation to the material while maintaining the shape of the metal rod, and ultrafine crystallization of the microstructure, thereby improving the mechanical properties of the material. .
또한, 본 발명의 비틀림 강소성 가공법은 표면 연마를 통해 기존 비틀림 변형보다 더 많은 양의 변형을 가하여 구배 정도 및 미세조직의 미세결정립화 정도를 향상시킬 수 있다.In addition, the torsional rigidity processing method of the present invention can improve the degree of gradient and the degree of microcrystallization of the microstructure by applying a larger amount of deformation than the conventional torsional deformation through surface polishing.
또한, 본 발명의 비틀림 강소성 가공법은 회전 속도를 조절하여 비틀림 변형의 조절 및 기계적 성질의 조절이 가능하다. In addition, the torsional rigidity processing method of the present invention is capable of controlling the torsional deformation and the mechanical properties by adjusting the rotational speed.
또한, 본 발명의 비틀림 강소성 가공법은, 금형의 회전수를 조절하여 재료에 가해지는 변형량을 자유자재로 조절할 수 있어 금속 봉재의 물성 강화 및 미세조직 조절에 용이하다.In addition, the torsionally rigid processing method of the present invention, by controlling the number of revolutions of the mold can be freely adjusted the amount of deformation applied to the material is easy to reinforce the physical properties of the metal bar and to control the microstructure.
이상에서 본 발명에 대한 기술 사상을 첨부 도면과 함께 서술하였지만, 이는 본 발명의 바람직한 실시예를 예시적으로 설명한 것이지 본 발명을 한정하는 것은 아니다. 또한, 이 기술 분야의 통상의 지식을 가진 자라면 누구나 본 발명의 기술 사상의 범주를 이탈하지 않는 범위 내에서 다양한 변형 및 모방이 가능함은 명백한 사실이다.Although the technical spirit of the present invention has been described above with reference to the accompanying drawings, the present invention has been described by way of example and is not intended to limit the present invention. In addition, it is obvious that any person skilled in the art may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (5)

  1. 금속 봉재에 비틀림을 가하는 공정; 및Twisting the metal rod; And
    상기 비틀림을 가하는 공정에 의해 상기 금속 봉재의 표면에 생성되는 표면 결함을 제거하는 공정을 포함하되,Including the step of removing the surface defects generated on the surface of the metal rod by the twisting process,
    상기 표면 결함을 제거하는 공정은, 상기 비틀림을 가하는 공정과 함께 이루어지는 연속 방식 또는 상기 비틀림을 가하는 공정을 일시적으로 중단하고 실시하는 단속 방식으로 수행하며,The step of removing the surface defects is carried out in a continuous manner in conjunction with the twisting step or in an intermittent way of temporarily stopping and executing the twisting step,
    상기 금속 봉재에 가해지는 비틀림 회전량 또는 전단 변형률을 증가시키는, 금속 봉재의 비틀림 강소성 가공법.Torsional rigid plastic working method of increasing the amount of torsional rotation or shear strain applied to the metal bar.
  2. 제1항에 있어서,The method of claim 1,
    상기 표면 결함을 제거하는 공정은 연마 공정을 포함하는, 금속 봉재의 비틀림 강소성 가공법.And a step of removing the surface defects comprises a polishing step.
  3. 제2항에 있어서,The method of claim 2,
    상기 연마 공정은 탄화규소(SiC) 연마지를 사용하는, 금속 봉재의 비틀림 강소성 가공법.The polishing step is a torsional rigid plastic working method of a metal bar using silicon carbide (SiC) abrasive paper.
  4. 제2항에 있어서,The method of claim 2,
    상기 연마 공정은 비틀림 회전량 또는 전단 변형률이 증가할수록 표면 거칠기가 감소하는 연마재를 사용하여 수행되는, 금속 봉재의 비틀림 강소성 가공법.Wherein the polishing process is performed using an abrasive material in which surface roughness decreases as the amount of torsional rotation or shear strain increases.
  5. 제4항에 있어서,The method of claim 4, wherein
    상기 연마 공정을 단속 방식으로 수행할 경우, 1회당 비틀림 공정 과정 중에 형성된 표면의 거칠기를 5㎛ 이하로 연마하는, 금속 봉재의 비틀림 강소성 가공법.When the polishing process is performed in an intermittent manner, the torsionally rigid plastic working method of the metal rod to polish the roughness of the surface formed during the twisting process per one time to 5㎛ or less.
PCT/KR2018/001541 2017-03-20 2018-02-06 Torsional severe plastic deformation method for metal bar, employing surface polishing to improve mechanical properties of metal bar WO2018174405A1 (en)

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