Ultimate Manufacturing Technology R and BD Group

Mungyeong, South Korea

Ultimate Manufacturing Technology R and BD Group

Mungyeong, South Korea
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Baek H.M.,KAIST | Hwang S.K.,Ultimate Manufacturing Technology R and BD Group | Joo H.S.,KAIST | Im Y.-T.,KAIST | And 2 more authors.
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2014

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. © 2014 The Korean Society of Mechanical Engineers.


Joo H.S.,KAIST | Hwang S.K.,Ultimate Manufacturing Technology R and BD Group | Baek H.M.,KAIST | Im Y.-T.,KAIST | And 2 more authors.
Procedia Engineering | Year: 2014

A non-circular drawing sequence was investigated for manufacturing medium carbon steel wires with improved spheroidization of cementite for better cold workability compared to those produced by the conventional wire drawing. The wire drawing and non-circular drawing processes with 20% area reduction per each pass were numerically and experimentally applied up to the fourth pass (total area reduction of 59%). The drawn wire by the non-circular drawing sequence shows higher average effective strain value than the one of the wire drawing in the numerical result. To investigate the effect of prior cold working on spheroidization of the drawn wire, spheroidization annealing was conducted at subcritical temperature of 705oC for 2 h for both processes. According to the present investigation, the wires subject to subcritical annealing following the non-circular drawing sequence showed the reduced ultimate tensile strength and micro-hardness, and the enhanced reduction of area compared to those for the wire drawing. From upsetting test results, cold workability was also improved for the annealed specimen processed by the non-circular drawing sequence compared to the one produced by the wire drawing. Scanning electron microscopy (SEM) was employed to investigate microstructure changes during spheroidization annealing. Owing to the SEM results, the spheroidization of the annealed specimens processed by the non-circular drawing sequence was improved than the one produced by the wire drawing. It is demonstrated that the non-circular drawing sequence could manufacture the wires with improved spheroidization of cementite and cold workability compared to the wire drawing in the present work. © 2014 The Authors. Published by Elsevier Ltd.


Joo H.S.,KAIST | Hwang S.K.,Ultimate Manufacturing Technology R and BD Group | Baek H.M.,KAIST | Im Y.-T.,KAIST | And 2 more authors.
Journal of Materials Processing Technology | Year: 2015

A non-circular drawing (NCD) sequence was applied as a prior cold working to improve spheroidization in a medium carbon steel wire. To investigate the effect of the NCD sequence on spheroidization behavior of the medium carbon steel wire, numerical simulations and experiments were carried out up to the fourth pass and were compared with the results of the conventional wire drawing (WD). From the three-dimensional numerical results, it was found that the NCD sequence could impose higher and relatively more homogeneous plastic deformation on the wire than the WD process. Spheroidization annealing at subcritical temperature of 705°C for 2, 4, and 8 h was applied for the specimens that were produced by the WD and NCD processes, respectively. Tension and Vickers micro-hardness tests were conducted to measure mechanical properties of the annealed specimens. The annealed specimen processed by the NCD sequence showed the reduced ultimate tensile strength and micro-hardness, and the enhanced reduction of area compared to those values for the WD process. According to upsetting test results, it was found that cold workability was also improved for the annealed specimen processed by the NCD process compared to the one produced by the WD process. Scanning electron microscopy (SEM) was employed to investigate the microstructure change and to quantitatively measure the spheroidization ratio of the annealed specimens processed by both processes. Owing to the SEM results, the spheroidization of the annealed specimens processed by the NCD sequence was improved compared to the one produced by the WD process. It can be construed from the current investigation that the NCD sequence might be helpful in improving the spheroidization of cementite and cold workability of medium carbon steel wires during the subcritical annealing. © 2014 Elsevier B.V. All rights reserved.


Lee S.-Y.,Ultimate Manufacturing Technology R and BD Group | Ko D.-C.,Pusan National University | Lee S.-K.,Ultimate Manufacturing Technology R and BD Group | Lee I.-K.,Ultimate Manufacturing Technology R and BD Group | And 3 more authors.
Advances in Mechanical Engineering | Year: 2014

In recent years, several studies with focus on developing state-of-the-art manufacturing technologies have been conducted to produce light vehicles by employing parts made of light materials such as aluminum and magnesium. Of such materials, magnesium has been found to pose numerous issues, because it cannot be deformed (plastic deformation) easily at low temperatures. Furthermore, oxidation on the surface of manganese occurs at high temperatures. This study analyzes the extrusion process for manufacturing magnesium bumper back beams used in vehicles, using finite element (FE) analysis. The properties of magnesium were determined through a compression test performed at high temperatures. And the temperature at which oxidation occurs at its surface was evaluated via an extrusion test. FE analysis was used to evaluate the extrusion load and temperature during the extrusion process, according to changes in initial material temperature and ram speed. Extrusion limit diagram of the extrusion process was derived based on the results of the FE analysis. Process conditions required to be established during the extrusion process were determined by using the derived extrusion limit diagram. The conditions were further validated by the extrusion test. © 2014 Sung-Yun Lee et al.

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