• Title/Summary/Keyword: Open-die forging

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Study on Manufacturing Process of Hollow Main Shaft by Open Die Forging (자유단조공법을 통한 중공형 메인샤프트 제조공정에 관한 연구)

  • Kwon, Yong Chul;Kang, Jong Hun;Kim, Sang Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.2
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    • pp.221-227
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    • 2016
  • The main shaft is one of the key components connecting the rotor hub and gear box of a wind power generator. Typically, main shafts are manufactured by open die forging method. However, the main shaft for large MW class wind generators is designed to be hollow in order to reduce the weight. Additionally, the main shafts are manufactured by a casting process. This study aims to develop a manufacturing process for hollow main shafts by the open die forging method. The design of a forging process for a solid main shaft and hollow shaft was prepared by an open die forging process design scheme. Finite element analyses were performed to obtain the flow stress by a hot compression test at different temperature and strain rates. The control parameters of each forging process, such as temperature and effective strain, were obtained and compared to predict the suitability of the hollow main shaft forging process. Finally, high productivity reflecting material utilization ratio, internal quality, shape, and dimension was verified by the prototypes manufactured by the proposed forging process for hollow main shafts.

An Experimental Study on Void Closure Behavior with respect to Reductions in Height (압하율에 따른 기공압착 거동에 관한 실험적 연구)

  • Choi, I.J.;Choi, H.J.;Park, H.J.;Choi, S.;Jung, T.W.;Park, D.K.;Choi, S.K.;Lim, S.J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.114-117
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    • 2009
  • In this work, closing behavior of the voids generated in a casting process was investigated for various parameters such as reductions in height void size and billet rotation during hot open die forging process. The reduction in height and path schedule including the number of paths and billet rotation were chosen as key process variables to express the change of geometrical void shape and void closing behavior. On the other hand, values of die overlapping and die width ratio were set to be constant. Extend of void closure was observed and evaluated using tensile test and microscope. Based on the experimental result, it is ensured that void closure do not occur at 15% and 30% reduction in height as well as one or two rotations of a billet. The useful datum obtained from this study could be utilized to establish an optimum path schedule in the open die forging process.

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Development of a Closed-die Design with Backpressure to Forge Rotating Scrolls (압축기용 구동스크롤의 밀폐형 배압 금형 개발)

  • Kim, Y.B.;Jung, K.H.;Lee, S.;Kim, E.;Lee, J.;Choi, D.S.;Lee, G.A.
    • Transactions of Materials Processing
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    • v.22 no.4
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    • pp.183-188
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    • 2013
  • Scroll compressors are widely used in air conditioning systems and in automobiles due to their low pressure loss, minimal vibrations, and light-weight. Open-die forging with back pressure is used to forge the rotating scroll, and it requires special care since the forging die can be severely damaged at the fixed end of the spiral cavity similar to a fracture of a cantilever beam. To overcome the inevitable weakness of the forging die due to such damage, an innovative design is necessary. In this study, structural analysis using the finite element method was conducted to determine the reason for the fracture of the forging die. A novel design to avoid stress concentrations and vertical deflection, causing serious damage to the die, is suggested.

Forging process design of cup shaped large forging using finite element method (유한요소해석을 통한 컵형상 대형단조품의 성형공법 설계)

  • Kang, Jong Hun;Kim, Hyun Jun;Lee, Hyoung Woo
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.7
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    • pp.729-734
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    • 2015
  • This research developed a new deep-bore, cup-shape, large forging process by combining die forging and free forging methods. In the proposed process, a preform for cup-shape large forging is produced by die forging, and a product with a deep bore is finally manufactured using an open die forging method, which is generally produced using a backward extrusion process. Finite element analysis results showed a higher effective strain distribution with a smaller forging load using the proposed method compared to the backward extrusion method. The production of a prototype with good internal quality using a small press capacity verified the proposed method.

The Incipient Deformation Analysis for Plane Strain Open-Die Forging Processes with V-shaped Dies Using the Force Balance Method (힘평형법을 이용한 V-형다이 평면변형 자유형 단조공정의 초기변형 해석)

  • Lee, J.H.;Kim, B.M.
    • Journal of the Korean Society for Precision Engineering
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    • v.10 no.4
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    • pp.109-117
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    • 1993
  • Force balance method is employed to predict forging information such as forging load, tool pressure and normal stress at the surface of tangential velocity discontinuity. The incipient stages of deformation for the plane strain forging of rectangular billets in V-shaped dies of different semi-angles are analysed. To construct an approximate model for the analysis of deformation by the force balance method in the incipient deformation stages, slip-line field is used. When the deformation mode by slip-line method is the same as that by force balance method, the slip-line method and the force balance method give identical solutions. The effects of die angle, coefficient of friction, billet geometries and deforma- tion characteristics are also investigated. In order to verify the validity of force balance analysis, the rigid-plastic finite element simulation for the various forgig parameters are performed and performed and find to be in good agreement.

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Influence of High Temperature Deformation Process Variables on the Microstructure and Thermo-physical Properties of a Ni-Fe-Co Alloy (Fe-Ni-Co 합금의 고온 변형 공정 변수와 미세조직 및 열물리적 특성의 상관 관계)

  • Yoon, D.H.;Jung, J.E.;Chang, Y.W.;Lee, J.H.;Lee, K.S.
    • Transactions of Materials Processing
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    • v.21 no.3
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    • pp.207-214
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    • 2012
  • High temperature deformation behavior of a $Ni_{30}Fe_{53}Co_{17}$ alloy, with its extraordinary low coefficient of thermal expansion less than $10{\times}10^{-6}K^{-1}$ at temperatures ranging from room temperature to 673K, was investigated by conducting a series of compression tests. From an empirical processing map, the appropriate working temperature-strain rate combination for optimum forming was deduced to be in the ~1373K, $10^{-2}s^{-1}$ region. This region has a relatively high power dissipation efficiency, greater than 0.36. Furthermore, open die forging of a 100mm diameter billets was performed to confirm the variation of thermo-physical properties in relation to microstructure. The coefficient of thermal expansion was found to increase considerably with increasing the open die forging temperature and decreasing the cooling rate, which in turn provides a drastic increase in the average grain size.

Evaluation methods for Void Closing Behavior in Large Ingot (기공닫힘부 폐쇄정도 결정을 위한 평가방법 연구)

  • Choi, I.J.;Choi, H.J.;Yoon, D.J.;Lee, G.A.;Lim, S.J.
    • Transactions of Materials Processing
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    • v.20 no.5
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    • pp.339-343
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    • 2011
  • This paper presents methods for analyzing the extent of cylindrical-shaped void closure. In addition, a quantitative relationship between change in void fraction and height reduction ratio of a compressed specimen is proposed. The height reduction ratio, number of deformation steps and billet rotation were chosen as key process parameters influencing the void closing behavior, namely, the changes in void shape and size during hot open die forging of a large ingot. The extent of void closure was analyzed from microscopic observations and estimated from tensile test results. The tensile strengths of specimens with closed voids and those without were compared for various reduction ratios in height. The results confirmed that void closure occurs at reduction ratios greater than 30 %. The void closing behavior could be expressed as a hyperbolic tangent function of reduction ratio in height, number of paths, and billet rotation. The knowledge presented in this paper could be helpful for optimizing deformation paths in open die forging processes.

The manufacturing process analysis and design of the forged turbine rotor by using the numerical analysis technique (수치해석 기법을 이용한 발전용 단조 로타의 제조 공정 분석 및 공정 설계)

  • 조종래;김동권;이정호;이부윤;이명렬
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1995.06a
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    • pp.25-34
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    • 1995
  • Large-scale low-alloy steel shafts, used in the manufacture of steam turbine, are produced by ingot making, forging and heat treatemtn processes. The numerical analysis techniques are introduced to analyze and design the working conditions in each process. The solidification of a steel ingot is studied through the finite element method. The open die press forging and quenching process are simulated by viscoplastic and elastic-plastic finite element method, respectively. Thus numerical analysis techniques are very useful tools to study favorable working conditions for better and more desirable product quality.

FE-Analysis on void closure behavior during hot open die forging process (열간 자유단조 공정시 내부 기공 압착 거동에 관한 해석)

  • Kwon, Y.C.;Lee, J.H.;Lee, S.W.;Jung, Y.S.;Kim, N.S.;Lee, Y.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2007.05a
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    • pp.160-164
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    • 2007
  • In the steel industry, there is a need to produce large forged parts for the automobile industries, the flight and shipping industries ad military industries. In the steel-industry application, a cogging technique for cast ingots is required, because the major parts are needed as one large body in order to obtain higher quality. Therefore, cogging process is the primary step in manufacturing of practically large open-die forging. In the cogging process, internal voids have to be eliminated as defects, The present work is concerned with the elimination of the internal voids in large ingots so as obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The FEM analysis are performed to investigate the overlap defect of cast ingots during cogging stage. The measure flow stress data were used to simulate the cogging process of cast ingot using the practical material properties. Also the analysis of void closure are performed by using the $DEFORM^{TM}$-3D. The calculated results of void closure behavior are compared with the measured results before and after cogging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the void closure can be investigated by the comparison of practical experiment and numerical analysis.

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A STUDY OF MAGNETIC ALIGNMENT OF DIE-UPSET Pr-Fe-B-Cu MAGNETS

  • Kwon, H.W.;Ma, T.J.;Harris, I.R.
    • Journal of the Korean Magnetics Society
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    • v.5 no.5
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    • pp.416-420
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    • 1995
  • An attempt has been made to investigate the mechanism of magnetic alignment in the magnets produced by upset forging the $Pr_{20}Fe_{74}B_{4}Cu_{2}$ cast bulk alloy. Upset forging of the cast alloy was carried out for 20 sec to an 80 % thickness reduction (strain rate : $4{$\times}10^{-2}s^{-1}$) in an open die configuration at varying temperatures in the range $600^{\circ}-900^{\circ}C$. It has been found that the upset forging process at temperatures above $800^{\circ}C$ can achieve a magnetic alignment to a great extent from copper-containing Pr-Fe- B-type cast ingot. The growth manner of the ferromagnetic $Pr_{2}Fe_{14}B$ matrix grain in Pr-Fe-B-type alloys was studied by examining the morphology change of the matrix grain in sintered body, and it was found that the matrix grains grew in anisotropic manner such that the grain grew more rapidly along the a- or b-axis than along the c-axis. This anisotropic grain growth led to the plate-like shape of the matrix grain. The magnetic alignment during the upset forging was attributed to grain boundary gliding of the plate-like grains, and the geometry of the grains in the cast ingot and the presence of a large amount of the praseodymium-rich grain boundary phase were thought to play a key role in the achievement of magnetic alignment.

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