• Title/Summary/Keyword: Drawability

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A Experimental Study of Cup forming by Stretch-Drawing Process (인장드로잉법에 의한 원통성형에 관한 실험적 연구)

  • 김영수
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2000.04a
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    • pp.123-128
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    • 2000
  • Fundamental and informative data of axi-symmetric stretch-drawing of several sheetmetals with thicknesses of 0.7-1.0mm are presented both for single and double operations. Very small radius is applied to the die profile (or-shoulder) ion all operations. to induce wall-thinning by the effect of bending-under-tension from which the name 'stretch-drawing' comes. It is clearly demonstrated that deeper cups could be formed by single and double stretch-drawings from smaller circular blanks due to such wall-thinning action than in the usual deep-drawing of larger blanks, From this fact it is emphasized that the deep-drawability of a sheet metal is not evaluated simply by the conventional L.D.R (limiting drawing ratio) but the depth of the drawn cup should also be taken into account./ Many experimental data about various metals and thicknesses given in this paper offer a valuable information in this process for more general use which recommends to replace the conventional deep-drawing process by the stretch-drawing process both for single and double operations. In the single stretch-drawing it is also confirmed that a deeper cup can be produced by raising the blank-holding force at later stage of operation.

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Asymmetric Rolling as Means of Texture and Ridging Control and Grain Refinement (집합조직과 이랑형표면결함의 제어 및 결정립 미세화 수단으로서의 비대칭압연)

  • Lee D.N.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.08a
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    • pp.11-18
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    • 2004
  • Asymmetric rolling, in which the circumferential velocities of the upper and lower rolls are different, can give rise to intense plastic shear strains and in turn shear deformation textures through the sheet thickness. The ideal shear deformation texture of fcc metals can be approximated by the <111> // ND and $\{001\}<110>$ orientations, among which the former improves the deep drawability. The ideal shear deformation texture for bcc metals can be approximated by the Goss $\{110\}<001>\;and\;\{112\}<111>$ orientations, among which the former improves the magnetic permeability along the <100> directions and is the prime orientation in grain oriented silicon steels. The intense shear strains can result in the grain refinement and hence improve mechanical properties. Steel sheets, especially ferritic stainless steel sheets, and aluminum alloy sheets may exhibit an undesirable surface roughening known as ridging or roping, when elongated along RD and TD, respectively. The ridging or roping is caused by differently oriented colonies, which are resulted from the <100> oriented columnar structure in ingots or billets, especially for ferritic stainless steels, that is not easily destroyed by the conventional rolling. The breakdown of columnar structure and the grain refinement can be achieved by asymmetric rolling, resulting in a decrease in the ridging problem.

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Developments and applications of high strength cold rolled steel sheets for automobiles (자동차용 고강도 냉연강판의 개발 및 적용현황)

  • Kim S. J.;Chin K. G.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.08a
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    • pp.45-52
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    • 2004
  • Continuing pressure for the weight reduction of vehicles and improvement of collision safety is driving the development of new high strength steel with excellent formability. The formable high strength steels which have excellent drawability have been developed and applied to the complicated inner panels. Although BH steel have mainly occupied the material market for outer panels, it is challenged by DP steel which have low yield strength and good bake hardenability. The advanced high strength steel, TRIP steels and DP steels which have excellent formability are new alternatives to conventional HSLA steel for structural parts such as members and pillars. HSLA steels also have been used for automotive bumper reinforcements due to their high yield ratio. Higher grade complex phase steel(CP) were developed for bumper reinforcements by addition of precipitation hardening to transformation strengthened steel. The usage of the advanced high strength steel ale increasing and will become the main material in structural parts near future. This paper describes the features of newly developed high strength cold rolled steels for automobiles.

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The Die Development of REF SILL OTR-R/L Auto-Body Panel by using Forming Analysis (성형해석을 통한 REF SILL OTR-R/L 차체판넬 금형개발)

  • Jung, D.W.;Lee, C.H.;Moon, W.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2006.06a
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    • pp.81-85
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    • 2006
  • The characteristic of sheet metal process is the few loss of material during process, the short processing time and the excellent price and strength. The sheet metal process with above characteristic is common used in industrial field, but in order to analysis irregular field problems the reliable and economical analysis method is demanded. Finite element method is very effective method to simulate the forming processes with good prediction of the deformation behaviour. Among Finite element method, The static-implicit finite element method is applied effectively to analyze real-size auto-body panel stamping processes, which include the forming stage. In this paper, it was focussed on the drawability factors on auto-body panel stamping by AUTOFORM with using tool planing alloy to reduce law price as well as high precision from Design Optimization of die. According to this study, the results of simulation will give engineers good information to access the Design Optimization of die.

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A Study on the Drawability of Clad Sheet Metal (STS304-A1050-STS304) by Warm Draw Die (온간금형에 의한 클래드판재(STS304-A1050-STS304)의 드로잉성 연구)

  • Ryu H. Y.;Kim J. H.;Ryu J. G.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2002.02a
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    • pp.136-143
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    • 2002
  • Warm draw die technique which is one of the new forming technologies to improve formability of sheet metal is applied to the cylindrical and square cup drawing of stainless-aluminum clad sheets. In experiments the temperature of die and blank holder is varied from room temperature to $180^{\circ}C$, while the punch is cooled by circulation of coolant to increase the fracture strength of workpiece on the punch comer area. Test materials chosen for experiments are STS304-A1050-STS304 clad sheets. Teflon film as a lubricant is used on both sides of a workpiece. The limit drawing ratio and relative drawing depth as well as quality of drawn cups(distribution of thickness)are investigated and validity of warm drawing process is also discussed. No separation between each laminated material after drawing occurred through inspection by microscope as well as application of penetrant remover and bond strength test. Therefore, warm forming technique was confirmed to give better results in deep drawing of stainless clad sheet metal.

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Improvement of the Stamping Formability by BHF Control (블랭크 홀딩력 제어에 의한 스탬핑 가공성 향상 기술)

  • 김영석;임성언;손형성;한수식
    • Transactions of Materials Processing
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    • v.8 no.3
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    • pp.269-275
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    • 1999
  • A variable blank holding force method is proposed to improve deep drawing characteristics of sheet materials. In this method, the blank holding force (BHF) is controlled throughout a drawing process so that the punch load does not exceed a critical value, which is slightly less than the conventional process with the conforming process with the variable BHF is more flexible than the conventional process with the constant BHF and it could be used for improving the product's quality and drawability. In this paper we suggest a method controlling the BHF as a function of punch travel during the forming process. The optimization BHF curves are determined theoretically and experimentally. It is concluded that for the case of optimum BHF control methods the drawn cup height and the drawing formability achieved by this method are increased than those for constant BHF method. Also, as comparing the wall thickness distribution of the cup drawn by the constant BHF and the optimum BHF control, the BHF control reduce the wall thickness variation of the drawn cup at the cup wall and make the cup thickness distribution more uniformly than the constant BHF.

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Changes in Microstructure and Texture during Annealing of 0.015% C-1.5% Mn-0~0.5% Mo Steels (0.015% C-1.5% Mn-0~0.5% Mo 강의 어닐링과정에서 미세조직과 집합조직의 변화)

  • Jeong, Woo Chang
    • Journal of the Korean Society for Heat Treatment
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    • v.24 no.5
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    • pp.251-261
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    • 2011
  • The changes in microstructure and texture during annealing were examined in a series of 0.015% C-1.5% Mn cold-rolled sheet steels with 0~0.5% Mo. Orientation distribution function data were calculated from the (110), (200), (211) pole figures determined on the rolled plane of cold-rolled and annealed steel sheets. Regardless of Mo content and annealing conditions, martensite volume fraction was less than 1.0%, not affecting the texture evolution. Textural change at the cooling stage after heating at $820^{\circ}C$ for 67 sec was not observed. Increasing the Mo content and annealing temperature markedly strengthened the intensities of ${\gamma}$-fiber texture, resulting in the increase in $r_m$ value. The desirable texture evolution for deep drawability in the 0.5% Mo steel may be mainly caused by the grain refining effect of Mo carbide in the hot-rolled steel sheet.

Effect of Processing Conditions on the Deep Drawability of Ti-6Al-4V Sheet at Warm Temperatures (Ti-6Al-4V판재의 온간 딥드로잉 성형성에 미치는 공정변수의 영향)

  • Shin, G.S.;Park, J.G.;Kim, J.H.;Kim, Y.S.;Park, Y.H.;Park, N.K.
    • Transactions of Materials Processing
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    • v.24 no.1
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    • pp.5-12
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    • 2015
  • In the current study, fundamental deep drawing characteristics of Ti-6Al-4V alloy sheets were investigated to establish the effect of processing conditions on large size square deep drawn cups. To accomplish this study, FE-simulations (Abaqus) were performed to determine optimum blank size, friction coefficient, the gap between punch and die, etc. The simulated processing parameters were verified experimentally. Based on the FE-simulation results, deep drawing was performed with various blank holding loads and sample sizes. In order to improve the formability of Ti-6Al-4V sheet, various lubricant methods were evaluated. Tensile tests and thickness measurements were conducted on the formed sheets. Processing parameters including blank holding force, lubricants, and optimum blank size, were selected to achieve improved drawing quality. With the optimum processing condition, a $200mm{\times}200mm$ cup was deep drawn successfully.

Textures Evolution of Rolled AA5182 Alloy Sheets after Annealing (알루미늄 5182 압연 판재의 어닐링 집합조직)

  • Kim Kee Joo;Shin Kwang Seon;Jeong Hyo-Tae;Paik Young-Nam
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.6
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    • pp.128-134
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    • 2005
  • In order to fabricate the aluminum alloys with good drawability, the textures evolution of the AA5182 sheets after rolling and annealing was studied. The measurement of the deformation textures was carried out for the sheets which were cold rolled with high reduction ratio by using the symmetric roll. In addition, the change of the recrystallization texture was investigated after heat-treatments of the rolled sheets with various heat treatment conditions. Rolling without lubrication and subsequent annealing led to the formation of favorable $rot-C_{ND}\;\{001\}<110>\;and\;{\gamma}-fiber ND//<111>$ textures in AA5182 sheets. From the results, the ${\gamma}$-fiber ND//<111> component well evolved during rolling at highest reduction ratio (over $90\%$, l/d parameter of 6.77). Among shear deformation textures, the ${\gamma}$-fiber ND//<111> was not rotated in holding time of $180\~7,200$ seconds at $350^{\circ}C$. The Monte-Carlo technique was used and could be representatively simulated these textures evolution during recrystallization.

Effects of Carbon and Sulfur Content on Mechanical Properties of High Purity Steel (고순도강의 기계적 성질에 미치는 탄소 및 황 함량의 영향)

  • Yoon, Jeong-Bong;Kim, Sung-Il;Kim, In-Bea
    • Korean Journal of Metals and Materials
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    • v.47 no.6
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    • pp.331-337
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    • 2009
  • To lower the annealing temperature and the deviation of the mechanical properties of bake hardening steels, high purity steels were investigated. The steels were characterized by treating at low recrystallization temperature. It was confirmed that the strengthening originated from the solid solution of carbon and the ferrite grain refinement by fine MnS precipitates as carbon and sulfur contents increased in high purity steels. However, it was observed that there was no more increase of strength in steels containing over 40 ppm of carbon. It was considered that the excess carbon formed either the carbon cluster or the low temperature unstable carbides which had the negligible effect on the strengthening because they were reported to be highly coherent with the matrix. The carbon cluster and unstable carbides could be transformed to the stable cementite during bake hardening treatment. MnS was not observed in the high purity steel containing 5 ppm S, resulting in very coarse recrystallized grains and good ductility. As sulfur content increased, the recrystallized grain size decreased due to the formation of the fine MnS precipitates.