The University of Osaka · 공학
Shotaro Yamashita 교수의 연구실은 용접 공정 중의 온도 분포 측정 및 열처리 거동 분석을 중심으로, 고속 레이저 용접 시의 비접촉 2차원 온도 측정 기술과 두색법 온도 측정 기반의 실시간 온도 분석 기법을 개발하고 있습니다. 특히, 고온 균열(고온균열, solidification 및 liquation cracking)의 발생 메커니즘을 해석하고, 용접 금속의 응고 거동과 열피로 특성에 영향을 미치는 합금 원소의 기여도를 규명하는 데 초점을 맞추고 있습니다. 이와 함께 Varestraint 시험을 활용한 고온 연성 곡선 모델링 및 비정상적 응력 분포의 영향 분석을 통해 용접 균열 예측 기반 기술을 발전시키고 있습니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
The aim of this study was to develop a temperature measurement technique during welding using a developed multi-sensor camera based on a two-color thermometry method. This technique has specific features, such as in-situ temperature measurement, high response speed, two-dimensional (2D) noncontact measurement, and flexibility. Accurate in-situ temperature 2D distribution and its history can be acquired based on the selection of a suitable combination of band-pass filters for laser welding and th
Abstract The hot cracking susceptibility in the Trans-Varestraint test was evaluated using the nominal strain calculated using the curvature radius of a bending block and the thickness of a specimen based on the theory of material mechanics. The nominal strain was calculated using the material properties at room temperature. Thus, in the Trans-Varestraint test, the non-uniformity of the strain around the weld part due to the temperature distribution is not considered. Therefore, the strain in th
Solidification cracking and liquation cracking susceptibility of four kinds of alloy 617 commercial filler metals were evaluated by Varestraint test, in order to clarify a fundamental effect of each solute element in the alloy. Fracture surface of cracking in alloy 617 multipass welds by GTA welding exhibited a possibility of occurrence of both solidification cracking and liquation cracking. Brittle temperature ranges (BTR) of the liquation cracking at each alloy were almost same, however the BT
The aim of this study is to develop the novel temperature measurement method during welding by using two high-speed cameras and the two-color thermometry method. This new method has some features, i.e. in-situ observation, high response speed, 2D measurement, wide temperature range and noncontact measurement. By using this method, the accurate in-situ temperature 2D distribution and history could be obtained during laser welding based on the selection of suitable band-pass filters for laser weld
The aim of this study is to discuss and model the hot ductility curve during solidification in the welding from the metallurgical point of view. The contents in this study are as follows. The transverse Varestraint test was conducted to evaluate the solidification cracking, then the in-situ observation was applied on the Varestraint test in order to obtain the critical strain of solidification cracking occurrence. In addition, the U-type hot cracking test was also carried out for obtaining the c
．そこで，本研究では梨形ビード割れの抑制を 炭素鋼の凝固割れ感受性に及ぼす溶質元素の影響
It is well known that the solidification cracking susceptibility of stainless steel changes depending on the amount of ferrite in the weld metal at room temperature. However, the cause and effect of the amount of ferrite at room temperature and solidification cracking have not always been clarified. When considering the temperature range in which solidification cracks occur, it must be necessary to focus on changes in microstructure and behavior during solidification. In this study, the solidifi
It is well-known that the solidification cracking susceptibility of stainless steel changes depending on the amount of ferrite in the weld metal at room temperature. However, the cause and effect of the amount of ferrite at room temperature and solidification cracking have not always been clarified. When considering the temperature range in which solidification cracks occur, it must be necessary to focus on changes in microstructure and behavior during solidification. In this study, the solidifi
Solidification cracking and liquation cracking susceptibility of four kinds of alloy 617 commercial filler metals were evaluated by Varestraint test, in order to clarify a fundamental effect of each solute element in the alloy. Fracture surface of cracking in alloy 617 multipass welds by GTA welding exhibited a possibility of occurrence of both solidification cracking and liquation cracking. Brittle temperature ranges (BTR) of the liquation cracking at each alloy were almost same, however the BT
This paper reports on the effect of carbon, silicon, manganese, chromium and aluminum on solidification cracking susceptibility of high manganese steel. The solidification cracking susceptibility of high manganese steel has been evaluated by using trans-Varestraint test and BTR that is one of the evaluation index of the solidification cracking susceptibility was obtained and compared. According to quenched microstructure observation by EPMA and EBSD analysis, solidification mode at all material
The aim of this study was to investigate the influence of welding parameters such as arc current, welding speed and wire feeding speed on the grain refining in weld metal of type 310S austenitic stainless steel. Besides, the effect of the grain refinement on mechanical properties such as tensile strength, hardness and ultrasonic transmission was examined. Equiaxed grains of about 15 μm formed by hot-wire GTAW in weld metal and the fine grain formed over a wide range stably. When the wire current
A growth rate of an intermetallic compound (IMC) composed of Fe and Al was evaluated to predict the distribution of IMC at the Fe/Al dissimilar material interface during laser brazing. A carbon steel crucible was made, then the aluminum alloy of braze material was melted in the crucible, and the IMC thickness formed at the Fe/Al solid-liquid interface was measured at heating temperatures between 750~900 ºC. EDS analysis revealed that the IMC at the interface was FeAl3 or Fe2Al5, the IMC growth f
The aim of this study was to elucidate the grain refinement mechanism in weld metal of type 310S stainless steel by hot-wire GTA welding. Quenched microstructure of weld pool during welding was obtained by liquid-tin and water quenching method. Microstructure evolution of wire during heating was investigated using hot-wire heating device.
