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오늘 본 자료
주호선(Ho Seon Joo),황선광(Sun Kwang Hwang),백현무(Hyun Moo Baek),임용택(Yong-Taek Im),손일헌(Il-Heon Son),배철민(Chul Min Bae) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
In the present study, a non-circular drawing (NCD) sequence was investigated for manufacturing medium carbon steel wires in which spheroidization of cementite was improved. The NCD was applied up to four passes and compared with the wire drawing (WD) process. According to the present investigation, the wires, subject to subcritical annealing following the NCD, showed the reduced ultimate tensile strength and the enhanced reduction of area compared to those for the WD process. Scanning electron microscopy was employed to investigate the underlying mechanism for such phenomena by observing the microstructure changes during the spheroidization annealing. It was found that the spheroidization of cementite was more likely to be accelerated by the NCD.
ECAP-Conform을 활용한 연속 하이브리드 공정 개선
주호선(H. S. Joo),황선광(S. K. Hwang),백현무(H. M. Baek),임용택(Y. T. Im),손일헌(I. H. Son),배철민(C. M. Bae) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
A continuous hybrid process is combined with wire-drawing, equal channel angular pressing (ECAP) and rolling process as a continuous severe plastic deformation technique to manufacture high-strength wires. In this study, ECAP Conform process was applied instead of ECAP and rolling processes in the continuous hybrid process to improve applicability of the process. The round groove in the feeding roll of the ECAP-Conform was used to manufacture circular shape wires. For verification of the designed process, finite element analysis was carried out with various shear friction factors of the workpiece with the given feeding roll and dies. This approach could be helpful in reducing the roll jumping and buckling involved with the continuous hybrid process.
황선광,백현무,주호선,임용택 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.2
In this work, a multi-pass continuous hybrid (CH) process was experimentally applied with up to five passeswith three processing routes, A, Bc, and C, to check the practicality of the processing routes and investigatetheir effect on the mechanical properties, microstructure, and texture evolutions of low-carbon steel wires. According to the present investigation, the wires processed by the 5th pass CH process with route A showed thehighest ultimate tensile strength value (762 MPa) compared to those for routes Bc (718 MPa) and C (720 MPa),respectively. Based on the compression test results, the CH processed wire showed good workability whenthe aspect ratio was smaller than 2.4 for all the processing routes. According to the microstructure and textureevolutions, the grain sizes of the 5th pass CH processed wires decreased for all the processing routes than that ofthe initial specimen, and the wires showed mixed texture distribution of shear and drawing texture components. From the present investigation, it was concluded that the processing routes of the CH process couldstrongly affect the microstructure and texture evolutions, resulting in changes of the mechanical propertiesand workability of the low-carbon steel wires.
음향방출센서를 이용한 선조질강(ESW90)의 압축실험에서의 표면 균열 발생 검출
이정음,이진명,주호선,서영호,김지훈,김상우 한국소성∙가공학회 2020 소성가공 : 한국소성가공학회지 Vol.29 No.1
In the design of the metal forming processes, various types of ductile fracture criteria are used to predict crack initiation and to fabricate metallic products without any defects. However, the quantitative measurement method for determination of crack initiation is insufficient. It is very difficult to detect crack initiation in ductile metals with excellent deformability because no significant load drop is observed due to crack generation. In this study, the applicability of acoustic emission sensors, which are commonly used in facility diagnostics, to measure crack initiation during the metal forming process was analyzed. Cylindrical notch specimens were designed using the finite element method to induce a premature crack on the surface of pre heat-treated steel (ESW90) material. In addition, specimens with various notch angles and heights were prepared and compression tests were carried out. During the compression tests, acoustic emission signal on the dies and images of the surface of the notch specimen were recorded using an optical camera in real time. The experimental results revealed that the acoustic emission sensor can be used to detect crack initiation in ductile metals due to severe plastic deformation
황선광(S. K. Hwang),백현무(H. M. Baek),주호선(H. S. Joo),김신회(S. H. Kim),임용택(Y. T. Im),손일헌(I. H. Son),배철민(C. M. Bae) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
In this work, a multi-pass continuous hybrid (CH) process is designed and its practicality is investigated for manufacturing high performing low-carbon steel wires in a continuous way. For this purpose, the multi-pass CH process was experimentally set up and applied up to five passes with route A at room temperature and was compared with those for the multi-pass wire drawing(WD) process. According to the present investigation, the grain-refined wires, which have many well defined high angle grain boundaries, with the enhanced ultimate tensile strength and comparable ductility were successfully produced by the five-pass CH process compared to the WD process. In addition, the fatigue limit of the specimen produced by the CH process was enhanced due to the grain-refined microstructure of the specimen compared to the one of the WD process. Based on these observations, it was found that the multi-pass CH process can effectively produce a fine-grained wire with enhanced mechanical properties compared to the WD process.
비원형 신선을 이용한 고강도-고연성 펄라이트 강선의 제조
백현무(Hyun Moo Baek),황선광(Sun Kwang Hwang),주호선(Ho Seon Joo),임용택(Yong-Taek Im),손일헌(Il-Heon Son),배철민(Chul Min Bae) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
In this study, a non-circular drawing (NCD) sequence was investigated for manufacturing high-strength and highductility pearlitic steel wires considering the effect of processing routes on occurrence of delamination fracture during the torsion test. For this purpose, the multi-pass NCD was conducted up to the 12th pass at room temperature with two kinds of processing routes, defined as the NCDA and NCDB. It was compared with the conventional wire drawing (WD). In the torsion test, delamination fracture was observed in the drawn wire by the WD for the 10th pass while it was not observed in the 12th pass NCDB. According to the X-ray diffraction measurement, a circular texture component, which increases likeliness of delamination fracture, was rarely observed in the drawn wire by the NCDB. From these results, it was demonstrated that the multi-pass NCDB could manufacture high-strength pearlitic steel wires with high-torsional ductility compared to the WD by reducing likeliness of delamination fracture.
비원형 신선을 이용한 고강도-고연성 펄라이트 강선의 제조
백현무(Hyun Moo Baek),황선광(Sun Kwang Hwang),주호선(Ho Seon Joo),임용택(Yong-Taek Im),손일헌(Il-Heon Son),배철민(Chul Min Bae) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.7
본 연구에서는 고강도-고연성 펄라이트 강선을 제조하기 위하여 비원형 신선 공정을 적용하였다. 다단 비원형 신선 공정을 A와 B로 정의한 2 종류의 가공경로를 이용하여 상온에서 12 패스까지 수행하였다. 비원형 신선 공정과의 비교를 위해서 기존의 원형 신선 공정을 수행하고 기계적 특성과 집합조직발달에 대해 비교를 수행하였다. 원형 신선 공정으로 제조된 강선은 10 패스에서부터 박리파괴가 관찰되었지만, 비원형 신선 가공경로 B의 경우는 12 패스에서도 박리파괴가 발생하지 않았으며, 이는 X-선회절로부터 측정된 집합조직 결과에서 원형집합조직의 발달이 적은 것과 연관된다. 따라서, 다단 비원형 신선 공정을 통하여 기존의 신선 공정보다 박리파괴의 발생 가능성을 저감시킴으로써 높은 비틀림 연성을 갖는 고강도 펄라이트 강선을 제조할 수 있음을 확인할 수 있었다. In this study, a noncircular drawing (NCD) sequence for manufacturing high-strength and high-ductility pearlitic steel wires was investigated. Multipass NCD was conducted up to the 12th pass at room temperature with two processing routes (defined as the NCDA and NCDB), and compared with the wire drawing (WD). During the torsion test, delamination fracture in the drawn wire was observed in the 10th pass of the WD whereas it was not observed until the 12th pass of the NCDB. From X-ray diffraction, the circular texture component that increases the likelihood of delamination fracture of the drawn wire was rarely observed in the NCDB. Thus, the improved ability of the multipass NCDB to manufacture high-strength pearlitic steel wires with high torsional ductility compared to the WD (by reducing the likelihood of delamination fracture) was demonstrated.