• Title/Summary/Keyword: Micro-rolling

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Effect of Alloying Composition and Plastic Deformation on the Microstructure of 22Cr Micro-Duplex Stainless Steel (합금원소와 소성변형이 22Cr 마이크로 듀플렉스 스테인리스강의 미세조직에 미치는 영향)

  • Park, Jun-Young;Ahn, Yong-Sik
    • Korean Journal of Metals and Materials
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    • v.50 no.11
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    • pp.793-800
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    • 2012
  • The effect of cold rolling on the microstructural evolution in 22Cr-0.2N micro-duplex stainless steel was investigated. The 22Cr-xNi-yMn-0.2N duplex stainless steel plates with various Ni and Mn contents were fabricated. The steels were vacuum induction melted and hot rolled, followed by annealing treatment at the temperature range of $1000-1100^{\circ}C$, in which both the austenite and ferrite phases were stable. The volume fraction of the ferrite phase depending on the alloy compositions of Ni and Mn increased with an increase in the annealing temperature. Grain growth in the ferrite phase occurred markedly after cold rolling followed by annealing, while fine recrystallised grains were still found in the austenite phase. A large number of martensite laths was found in the microstructure of cold rolled steels, which should be formed by strain-induced martensite from the austenite phase. The intersections of stacking faults were revealed by TEM observation. The volume fraction of the martensite phase increased with an increase of the reduction ratio by cold rolling.

Development of a micro-scale Y-Zr-O oxide-dispersion-strengthened steel fabricated via vacuum induction melting and electro-slag remelting

  • Qiu, Guoxing;Zhan, Dongping;Li, Changsheng;Qi, Min;Jiang, Zhouhua;Zhang, Huishu
    • Nuclear Engineering and Technology
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    • v.51 no.6
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    • pp.1589-1595
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    • 2019
  • In this paper, the CLAM steel strengthened by micro-scale Y-Zr-O was prepared by vacuum induction melting followed by electroslag remelting (VIM-ESR). Yttrium (Y) and zirconium (Zr) were easy to aggregates into massive yttrium-zirconium-rich inclusions in the steel melted by vacuum induction melting (VIM), which would interrupt the continuity of the matrix and reduce the mechanical properties of steel. Micron-sized Y-Zr-O inclusions would be produced with the removal of original blocky Y-Zr-rich inclusions and the submicron-sized inclusions smaller than $0.2{\mu}m$ could be retained in the steel. The small grain size and the better refinement and distribution uniformity of Y-Zr-O inclusions after remelting would be responsible for the better yield strength and toughness. For VIM-ESR alloy, the ultimate tensile strength is 749 MPa and the yield strength is 642 MPa at room temperature, meanwhile they are 391 MPa and 367 MPa at $600^{\circ}C$, respectively. Meanwhile, the ductile-brittle transition temperature (DBTT) reduced from $-43^{\circ}C$ (VIM) to $-76^{\circ}C$ (VIM-ESR).

Wrinkle Defect of Low Carbon Steel in Wire Rod Rolling (저탄소강 선재 압연의 주름성 결함)

  • Kim H. Y.;Kwon H. C.;Byon S. M.;Park H. D.;Im Y. T.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.08a
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    • pp.307-316
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    • 2004
  • This study examined the cause of the wrinkle defect which is frequently encountered in wire rod rolling of low carbon steel$(C0.08\~0.13wt.\%)$. Even a small defect on the surface of rolled bars can easily develop into fatal cracks during cold heading process of low carbon steel, and it is therefore necessary to minimize inherent defects on the surface of hot rolled bars. Hot rolling process of low carbon steel was analyzed to identify the cause of the wrinkle defect in conjunction with FE analysis. The integrated analysis revealed that the wrinkle defect initiated in the first stage of rolling, and it was at the billet edge where severe deformation and drastic temperature drop were present. To elucidate the micro-mechanical mechanism of the wrinkle defect, hot compression tests were carried out at various temperatures and strain rates using Gleeble-3800. The surface profile of the each other compressed specimens was compared, and rough surface lines were observed at relatively low temperatures. Those surface defects can develop into wrinkles during multi-pass rolling. To control the wrinkle defect in rolling, it is necessary to design an adequate caliber which can minimize the loss of ductility, and thereby prevent flow localization. To use the result of this study fur other steels, the quantitative measure of the wrinkle defect and flow localization parameter should be proposed.

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Effect of Water Contamination of the Lubricant and Surface Roughness of Bearing Steel on the Rolling Contact Fatigue Life (윤활유의 수분혼입 및 베어링강의 표면 조도가 구름접촉 피로수명에 미치는 효과)

  • Heo, Tae Hyeon;Sim, Chung-Ki;Kim, Hong Seok;Shin, Ki-Hoon;Cheong, Seong Kyun
    • Journal of the Korean Society of Safety
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    • v.32 no.1
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    • pp.15-20
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    • 2017
  • A large amount of research has been performed on the rolling contact fatigue(RCF) life of bearings, since it directly affects the safety and reliability of mechanical systems. It is well known that rolling contact fatigue life is influenced by several parameters including contact pressure, oil contamination by water or metal particles, and the surface conditions of bearings. However, the detailed damage mechanisms involved in rolling contact fatigue have not been clearly identified yet. In this paper the effects of water contamination of the lubricant and surface roughness of bearing steel on the rolling contact fatigue life were investigated. Two types of specimens with different surface roughness values were prepared through turning and lapping operations. They were tested under two different lubrication conditions, i.e. oil lubricant with 100% of oil and the water contaminated condition with 80% of oil and 20% of water using the rolling contact fatigue testing machine. The surface damage induced by the rolling contact fatigue was observed by using atomic force microscope(AFM). Experimental results show that the rolling contact fatigue life, $L_{10}$ was reduced by 24 to 33% depending on the lubrication condition. The reduction of fatigue life in the range of 53 to 57% was also observed at different surface roughness conditions.

Evaluation on Microstructure and Mechanical Properties of Severely Deformed Pure Cu (강가공된 순수 Cu의 미세조직과 기계적 특성 평가)

  • Song, Kuk-Hyun;Son, Hyun-Taek;Kim, Dae-Keun;Kim, Han-Sol;Kim, Won-Yong
    • Korean Journal of Materials Research
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    • v.21 no.5
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    • pp.263-267
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    • 2011
  • The present study was carried out to evaluate the microstructural and mechanical properties of cross-roll rolled pure copper sheets, and the results were compared with those obtained for conventionally rolled sheets. For this work, pure copper (99.99 mass%) sheets with thickness of 5 mm were prepared as the starting material. The sheets were cold rolled to 90% thickness reduction and subsequently annealed at $400^{\circ}C$ for 30 min. Also, to analyze the grain boundary character distributions (GBCDs) on the materials, the electron back-scattered diffraction (EBSD) technique was introduced. The resulting cold-rolled and annealed sheets had considerably finer grains than the initial sheets with an average size of 100 ${\mu}M$. In particular, the average grain size became smaller by cross-roll rolling (6.5 ${\mu}M$) than by conventional rolling (9.8 ${\mu}M$). These grain refinements directly led to enhanced mechanical properties such as Vickers micro-hardness and tensile strength, and thus the values showed greater increases upon cross-roll rolling process than after conventional rolling. Furthermore, the texture development of <112>//ND in the cross-roll rolling processed material provided greater enhancement of mechanical properties relative to the case of the conventional rolling processed material. In the present study, we systematically discuss the enhancement of mechanical properties in terms of grain refinement and texture distribution developed by the different rolling processes.

Development of Technique Predicting of the Wear of DCI Roll Using Carbon Steel in Hot Rod Rolling Process (탄소강 선재 압연공정의 DCI 롤 마멸 예측 기술의 개발)

  • Kim, Dong-Hwan;Kim, Byeong-Min;Lee, Yeong-Seok;Yu, Seon-Jun;Ju, Ung-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.9
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    • pp.1736-1745
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    • 2002
  • The objective of this study is to predict the roll wear in hot rod rolling process. In this study hot rod rolling process for round and oval passes has been investigated. In order to predict the roll wear, the wear model is reformulated as an incremental form and then wear depth of roll is calculated at each deformation step on contact area using the results of finite element analysis, such as relative sliding velocity and normal pressure at contact area. Archard's wear model was applied to predict the roll wear. To know the thermal softening of DCI (Ductile Cast Iron) roll according to operating conditions, high temperature micro hardness test is executed and a new wear model has been proposed by considering the thermal softening of DCI roll expressed in terms of the main tempering parameter curve. 3D wear program developed in this study might be used for adjusting the gap of rolls to set up a suitable rolling schedule for keeping dimensional tolerance of the product.

Prediction of defect shape change using multiple scale modeling during wire rod rolling process (멀티 스케일 모델을 적용한 선재 공정의 미세결함 형상 변화 예측)

  • Kwak, Eun-Jeong;Kang, Gyeong-Pil;Lee, Kyung-Hoon;Son, Il-Heon
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.10a
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    • pp.169-172
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    • 2009
  • Multiple scale modeling has been applied to predict defect shape change during the wire rod rolling process. The size difference between bloom and defect prevent using usual FEM approaches due to the enormous number of elements required to depict the defect. The newly developed multiple scale model can visualize defect shape changes during the multi stands rolling process. The defect positioned at the top and side of bloom are smoothed out but the one at the middle evolved as folding or remained as crack. This approach can be used for defect control with roll shape design and initial bloom shape.

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Adjustment of Roll Gap for The Dimension Accuracy of Bar in Hot Bar Rolling Process (열간 선재 압연제품의 치수정밀도 향상을 위한 롤 갭 조정)

  • Kim, Dong-Hwan;Kim, Byung-Min;Lee, Young-Seog
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.6
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    • pp.96-103
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    • 2002
  • The objective of this study is to adjust the roll gap fur the dimension accuracy of bar in hot bar rolling process considering roll wear. In this study hot bar rolling processes fur round and oval passes have been investigated. In order to predict the roll wear, the wear model is reformulated as an incremental from and then wear depth of roll is calculated at each deformation step on contact area using the results of finite element analysis, such as relative sliding velocity and normal pressure at contact area. Archard's wear model was applied to predict the roll wear. To know the effects of thermal softening of DCI (Ductile Cast Iron) roll material according to operating conditions, high temperature micro hardness test is executed and a new wear model has been proposed by considering the thermal softening of DCI roll expressed in terms of the main tempering curve. The new technique developed in this study for adjusting roll gap can give more systematically and economically feasible means to improve the dimension accuracy of bar with full usefulness and generality.

Adjustment of Roll Gap for the Dimension Accuracy of Bar in Hot Bar Rolling Process

  • Kim, Dong-Hwan;Kim, Byung-Min;Lee, Youngseog
    • International Journal of Precision Engineering and Manufacturing
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    • v.4 no.1
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    • pp.56-62
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    • 2003
  • The objective of this study is to adjust the roll gap for the dimension accuracy of bar in hot bar rolling process considering roll wear. In this study hot bar rolling processes for round and oval passes have been investigated. In order to predict the roll wear, the wear model is reformulated as an incremental form and then wear depth of roll is calculated at each deformation step on contact area using the results of finite element analysis, such as relative sliding velocity and normal pressure at contact area. Archard's wear model was applied to predict the roll wear. To know the effects of thermal softening of DCI (Ductile Cast Iron) roll material according to operating conditions, high temperature micro hardness test is executed and a new wear model has been proposed by considering the thermal softening of DCI roll expressed in terms of the main tempering curve. The new technique developed in this study for adjusting roll gap can give more systematically and economically feasible means to improve the dimension accuracy of bar with full usefulness and generality.

Adjustment Of Roll Gap For The Dimension Accuracy Of Bar In Hot Bar Rolling Process (열간 선재 압연제품의 치수정밀도 향상을 위한 롤 갭 조정)

  • 김동환;김병민;이영석;유선준;주웅용
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.1036-1041
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    • 1997
  • The objective of this study is to adjust the roll gap for the dimension accuracy of bar in hot bar rolling process considering roll wear. In this study hot bar rolling processes for round and oval passes have been investigated. In order to predict the roll wear, the wear model is reformulated as an incremental form and then wear depth of roll is calculated at each deformation step on contact area using the results of finite element analysis, such as relative sliding velocity and normal pressure at contact area. Archard's wear model was applied to predict the roll wear. To know the effects of thermal softening of DCI (Ductile Cast Iron) roll material according to operating conditions, high temperature micro hardness test is executed and a new wear model has been proposed by considering the thermal softening of DCI roll expressed in terms of the main tempering curve. The new technique developed in this study for adjusting roll gap can give more systematically and economically feasible means to improve the dimension accuracy of bar with full usefulness and generality.

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