http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
강기석(Ki-Sok KANG),최영수(Young-Soo CHOI),이재향(Jae-Hyang LEE),남대근(Dae-Keun NAM) 한국철도학회 2016 한국철도학회 학술발표대회논문집 Vol.2016 No.10
KTX 열차의 기계제동장치인 제동디스크는 심한 압력과 열응력을 받아 과열 냉각이 반복적으로 일어남에 따라 균열이 발생하고 있다. 균열의 한도가 기준을 초과하면 열차에서 분리하여 균열부가 사라질 때까지 디스크를 삭정하거나 폐기 한다. 삭정 등으로 인한 손실을 줄이기 위해 디스크 균열부위의 재생 방법을 몇 가지 검토 적용한 결과 용접 재생 기술을 확보하였다. 이렇게 확보된 용접기술로 재생한 제동디스크를 고속차량에 적용하여 운행한 결과 특이사항이 발견되지 않았으며, 용접 재생 디스크를 한국화학융합시험연구원(KTR)에서 특성시험 분석결과 기준 값을 만족하였다. 제동디스크 용접재생기술로 고속차량 유지보수의 효율성을 높이고 신품 구입비용을 감소시켜 경영효율화에도 기여할 것으로 기대된다. Cracks on the brake discs of KTX often occurring by repetition of the cooling and overheating due to severe press and thermal stresses. If the cracks exceed the limits, we have to separate the brake discs from the train and repair by turning or dispose permanently. For saving the discs repairing budget, we found a new welding technique through a number of experiments. After repairing the discs by our new welding technique, we have completed test run with KTX trains successfully and satisfied standards set by the Korea Testing & Research Institute(KTR). We expect improvement on efficient brake disc regeneration and reducing significantly the purchase cost of new equipment.
저합금강의 인코넬 625 육성용접 후 열처리에 따른 미세조직 및 기계적 특성
김승필 ( Seung Pil Kim ),장재호 ( Jae Ho Jang ),김정수 ( Jung Soo Kim ),김병준 ( Byung Jun Kim ),손근용 ( Keun Yong Sohn ),남대근 ( Dae-geun Nam ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.8
Overlay welding technique is one of methods used to improve metal mechanical properties such as strength, toughness and corrosion resistance. Generally, Inconel 625 alloy is used for overlay welding layer on low carbon steels for economic consideration. However, the method produces some problems in the microstructure of the cast structure and some defects, caused by the elevated temperatures of the overlay welding process. To resolve these problems, heat treatments are required. In this study, Inconel 625 alloy was welded on a low carbon steel by the overlay welding process to investigate the resulting microstructure and mechanical properties. A double heat treatment was performed to improve the mechanical properties of the welding and substrate layers. It was found that Inconel 625 alloy had an austenite microstructure after the first heat treatment, but the low carbon steel had a ferrite-pearlite microstructure after the second heat treatment. After the double heat treatment, the sample showed the optimum hardness because of grain refinement and homogenization of the microstructure. (Received October 23, 2015; Accepted February 29, 2016)
저합금강의 이중 오스테나이징 템퍼링에서 냉각 속도에 따른 미세조직 및 기계적 특성 변화
김경후 ( Gyeong-hoo Kim ),장재호 ( Jae-ho Jang ),김성환 ( Sung-hwan Kim ),김병준 ( Byung-jun Kim ),손근용 ( Keun-yong Sohn ),남대근 ( Dae-geun Nam ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.8
Spent nuclear fuel is stored and transported in cask bodies, but they become embrittled with the passage of time resulting in lattice defects due to neutron irradiation. Cask bodies made by the quenching and tempering (QT) treatment are not safe and are hard to store because of embrittlement caused by high levels of radiation and heat over long periods. Recently, it was shown that the double austenitizing tempering (DAT) treatment resulted in a significant improvement in strength and toughness as a result of austenite grain refinement. In this study, we evaluated the effects of DAT treatment for improving the mechanical properties of low alloy steel. We also investigated the effects of cooling rate on the DAT treatment. It was found that the charpy impact properties of the alloy were improved by the DAT treatment, which used water cooling comparing, compared to the QT heat treated specimen. As a result of microstructure analysis, it was determined that the grain size and carbide morphology were affected by mechanical properties such as the tensile, hardness and impact property. (Received January 20, 2017; Accepted March 24, 2017)
STS304의 후열처리에 따른 용접부 미세조직과 기계적 특성 평가
장대한 ( Daehan Jang ),김광윤 ( Kwangyoon Kim ),김형찬 ( Hyoung Chan Kim ),전종배 ( Jong Bae Jeon ),남대근 ( Dae-geun Nam ),손근용 ( Keun Yong Sohn ),김병준 ( Byung Jun Kim ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.9
Abstract: Austenitic stainless steels have excellent mechanical property and corrosion resistance, and are for these reasons used in demanding applications such as power plant, nuclear reactor and off-shore plant. Especially, austenitic stainless steel 304 (STS304) is mainly used as a pipe material in nuclear power plants. Submerged arc welding (SAW) is a commonly used method of welded steel pipes. This method has some problems of microstructure and mechanical properties such as heterogeneous microstructure, ductility decreases, brittleness of a weld region after SAW process. Especially, delta ferrite and dendrite structure is happened in the weld metal after welding process, which affects the decrease of toughness and ductility. Therefore, it requires the post weld heat treatment (PWHT) in order to solve these problems. In this study, welded STS304 was investigate the microstructure and mechanical properties after SAW process. In order to improve the toughness and ductility of weld region, PWHT was performed by controlling the delta-ferrite and dendrite structure. It was found that the mechanical property of the weld region were increased due to the decrease of the delta- ferrite and the recrystallization of the austenite structure after PWHT. (Received March 30, 2017; Accepted May 31, 2017)