• 열처리공학회지
• /
• 제8권2호
• /
• pp.101-112
• /
• 1995

A study was made to examine the effects of heat-treatment on the microstructures of Cu-bearing HSLA steels. The details of microstructures were studied by using optical microscopy(OM), transmission electron microscopy(TEM) and hardness test. The as-rolled microstructure of HSLA-A consists of ferrite (${\alpha}$) whereas that of HSLA-B consists of needle-shaped phase. The difference in microstructure can be ascribed to the different amount of Ni, Mn, Mo, Cu which affect the hardenability. The austenite grain size is very small up to $1000^{\circ}C$ owing to the Nb-precipitates. As the austenitizing temperature increases above $1000^{\circ}C$, the austenite grain grows rapidly. There are two hardness peaks in the hardness versus temperature curve, at $500^{\circ}C$ and at $675^{\circ}C$ (HSLA-A), $725^{\circ}C$ (HSLA-B). The peak at $500^{\circ}C$ result from the formation of Cu-precipitates and second hardness peak is created due to the formation of M-A constituents. The hardriess decrease in HSLA-B steel with ageing temperature is small because of the higher amounts of Cu than HSLA-A steel. The fine, round ${\varepsilon}$-Cu precipitates grow with ageing temperature and finally transform into rod shape.

• Journal of Welding and Joining
• /
• 제27권4호
• /
• pp.73-78
• /
• 2009

Characterization of the microweld CCFL electrode for the TFT-LCD backlight unit was carried out in terms of the glass beading heat treatment conditions. We evaluate the weld zone and parent metal of the microweld CCFL electrodes that were exposed to simulated glass beading heat treatment. The CCFL electrode was composed of the cup made with pure Ni, the pin made with pure Mo and the lead wire made with Ni-Mn alloy. Each part of the electrode was assembled together by micro spot welding process and then the assembled electrodes were exposed to simulated glass beading temperatures of $700^{\circ}C,\;750^{\circ}C$ and $800^{\circ}C$. The microstructures of the microweld CCFL electrode were observed by using optical microscope, scanning electron microscope and EDS. Micro-tensile and microhardness test were also carried out. The results indicated that the grain coarsening in the HAZs(heat affected zones) for both the cup-pin weld and pin-lead wire were exhibited and the grain coarsening of the HAZ for the cup and the lead wire was more obvious than the HAZ of the pin. The micro-tensile test revealed that the fracture occurred at the cup-pin weld zone for all test conditions. The fracture surface could be classified into two parts such as pin portion and cup portion including weld nugget. The failure was seemed to be initiated from the boundary between nugget and pin through the weld joint. The result of the microhardness measurement exhibited that the relatively low hardness value, about 105HV was recorded at the HAZ of the cup. This value was about 50% less than that of the original value of the cup. The reduction of the microhardness was considered as the cause of the grain coarsening due to welding process. It was also appeared that there was no change in electric resistance for the standard electrodes and heat treated electrodes.

• 자원환경지질
• /
• 제47권4호
• /
• pp.351-362
• /
• 2014

미얀마 북서부 보피붐 크롬-광화대에 대한 지질특성, 광체산상 및 개발 잠재성을 파악하기 위하여 광화대내 약 $6km^2$ 탐사지역을 설정하여 한국지질자원연구원과 미얀마 지질조사광물탐사국이 현지 공동조사를 수행하였다. 조사지역 내 크롬광체는 주로 더나이트에 수반된 크롬철석암으로 해발 200-400 m 구간에 걸쳐 지표상에 분포하고 있는 것을 확인하였으며 지표지질 및 광상조사를 수행하여 1:1,000 축척의 정밀 지질도 및 광상분포도를 작성하였다. 지질 및 광상 조사와 병행하여 토양 지화학 탐사를 수행하였으며, 50 m 간격으로 총 114개 지점에 대한 피팅탐사를 실시하여 토양과 노두시료를 채취 분석 하였고, ICP-AES를 이용하여 Cr, Ni, Fe, Mn에 대한 지화학이상대도를 작성하였다.

• 한국환경보건학회:학술대회논문집
• /
• 한국환경보건학회 2005년도 Proceedings of KSEH.Minamata Forum
• /
• pp.87-94
• /
• 2005

Results from previous studies revealed that metal level in the body is related to certain types of diseases. For example. serum copper level with chronic heart failure, iron and transferrin in the blood serum with acute cerebral vascular diseases, Zn in the CNS, lead with neurotoxicity, hypertension, genetic damage, arsenic with cancer skin lesion, Al with neurobehavioral function (cognitive impairment and memory disorder), and etc. The rate of stroke has increased in recent years and several metals were found to be responsible for causing stroke. This study compared several blood metal concentrations between stroke and non-stroke patients. Patients with stroke (116 samples) and non-stroke (111 samples including lowback pain and others) participated in this study. Total of 227 blood samples were collected and participants completed questionnaires regarding age, gender, occupation, residence, alcohol, smoking, and etc. To be qualified into the stroke group, patients have never experienced stroke previously. Subjects only included ischemic stroke and intracerebral hemorrhage patients diagnosed by brain CT and brain MRI. Patients with high risk of metal exposure such as herbal intake and job related exposure were excluded. 10ml of blood samples were analyzed by ICP-MS method at the Center of Nature and Science at Sangji University. Metal geometric mean (SD) concentrations in blood of study subjects showed higher values, 2.64-36.12%, than WHO reference values in Mn, Ni, Hg, Se, and As. Metal concentration in blood of stroke patients non-adjusted for potential confounders was higher except for Hg and also higher except for Ni in adjusted for potential confounders. Co was significantly higher in stroke patients (p=0.002) than non-stroke patients adjusted for potential confounders. Regression coefficient values of stroke patients was 0.17-8.25 in each metals. Odd ratio of stroke patients had 0.96 (Ni)-2.68 (Co) compared to non-stroke cases. This result means that Co increase of 1 raises the risk ratio of stroke by 2.86 times. Based on the results, metal concentration in blood seems to affect incidence of stroke.

• 한국재료학회지
• /
• 제7권3호
• /
• pp.218-223
• /
• 1997

과냉각액체구역(${\Delta}T_{x}=T_{x}-T_{g}$)을 갖는 $Fe_{80}P_{10}C_{6}B_{4}$ 조성에 천이금속(Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Ni, Pd, Pt및 Cu)를 첨가하여 이들 원소가 유리화온도($T_{g}$), 결정화온도($T_{x}$) 및 과냉액체구역 (${\Delta}T_{x}$)에 미치는 영향에 \ulcorner여 조사하였다. $Fe_{80}P_{10}C_{6}B_{4}$ 합금의 ${\Delta}T_{x}$ 값은 27K였으나 이 합금에 Hf, Ta 및 Mo을 각각 4at%첨가하면 그 값이 40k 이상으로 증가하였다. 이같은 ${\Delta}T_{x}$ 값의 증가는 유리화온도($T_{g}$의 상승보다 결정화온도($T_{x}$)의 상승폭이 크기 때문이다. $T_{g}$ 및 $T_{x}$는 외각전자밀도(e/a)가 약 7.38에서 7.05로 감소할수록 상승하였다. e/a의 감소는 천이금속과 다른 구성원소(반금속)사이의 상호결합상태를 의미한다. 즉 $T_{g}$ 및 $T_{x}$의 상승은 강한 상호결합력에 기인하는 것으로 사료된다.

• 한국환경과학회지
• /
• 제24권2호
• /
• pp.175-188
• /
• 2015

For 63 soil series distributed in Jeju Island, natural uncultivated soils in each soil series were collected, and their physicochemical properties and their concentrations of 19 heavy metals including 8 heavy metals which are regulated by Korean Soil Environment Conservation Law, were analyzed. Moreover, the correlations between physicochemical properties and heavy metal concentrations, and between heavy metal concentrations were analyzed. The heavy metals distributed in the higher concentrations and the lower concentrations with arithmetric mean value, were Mn(730 mg/kg) and Ba(493 mg/kg), and Hg(0.146 mg/kg) and Tl(0.096 mg/kg), respectively. The correlations between pH($H_2O$) and heavy metals(Hg, Ni, Co, Se), between pH(NaF) and heavy metals(Hg, Ba, Se, Tl), and between organic matter content and heavy metals(Hg, Tl) were significant at the 0.01 level. From the correlations between heavy metal concentrations, there were 22 where there were significant at the 0.01 level and they showed positive correlation. Among those, the heavy metals showing the correlation higher than r=0.5, were Sb-V(0.878), Mo-Sn(0.867), Co-V(0.654), Co-Sb(0.648), Be-Sn(0.546), and Sn-Tl(0.528).

• 한국환경보건학회지
• /
• 제32권3호
• /
• pp.199-206
• /
• 2006

Various heavy metals have been known for causing ischemic stroke. In order to describe the causative relationship between the blood levels of various heavy metals and stroke patients, 116 patients with stroke and 111 patients without stroke were selected from one Oriental medical hospital in Wonju, Korea. Total of 9 kinds of metals such as As, Cd, Co, Cu, Hg, Mn, Ni, Pb, and Zn were analyzed in blood from patients with and without stroke. There were no significant differences in the means of metal concentrations between the stroke and nonstroke patients except for the mean of Co concentration. In the case of Co, the means for stroke and non-stroke patients were 0.44 ug/l and 0.40 ug/l showing a significant difference at the level of p-value=0.05. The odds ratios for each metal ranged from 0.96 to 2.86. Most odds ratios were not significant but the odds ratio for Co, $2.86{\pm}1.49$ was significant, indicating that Co increases the risk of stroke by 2.86 times. In order to identify the specific risk level of stroke increased by a multiple interaction of metals, regression coefficients and odds ratio for a pair or multiple pair of metals were reanalyzed. However, all of regression coefficients and odds ratios were not significant. In conclusion, Co showed the significant level in blood from patients with stroke. In addition, the odds ratio of stroke was significantly different from other metals. Thus, it is considered that Co among various metals analyzed in this study is the important metal for increasing the risk of stroke.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제18권7호
• /
• pp.32-40
• /
• 2013

This study was objected to evaluate the potential impact on the groundwater environment of the coal bottom ash used as fill materials on the land surface. From four coal-fired power plants, bottom-ashes were collected and analyzed through sequential extraction and column leaching tests following the meteoric water mobility procedure. The column tests shown leaching heavy metals including Pb, As, B, Cu, Zn, Mn, Ni, Ba, Sr, Sb, V, Cr, Mo, and Hg. The relatively high concentrations of B, Sr, Ba, and V in leachate were attributed to both the higher concentrations in the bottom ash and the relatively higher portion of leachable state, sorbed state, of metals. Bottom-ash samples from the D-plant only show high leaching potential of sulfate ($SO_4$), probably originated from the coal-combustion process, called the Fluidized Bed Combustion. Consequently, to manage recycling bottom ashes as fill materials, an evaluation system should be implemented to test the leaching potentials of metals from the ashes considering the absolute amount of metals and their state of existence in ashes, and the coal-combustion process.

• 한국주조공학회지
• /
• 제37권1호
• /
• pp.21-29
• /
• 2017

The effects of W content and heat treatment on the microstructure and mechanical properties of Hastelloy C-276 alloy investment castings were discussed. As the W content was increased, dendritic microstructure was refined and network type precipitate formed during solidification was distributed on the dendritic grain boundaries. Cr, Fe and Mn were highly segregated in the Ni-based dendrite matrix, and Mo, W, C and Si were in the precipitates. Due to the heat treatment, fine granular and flake precipitates were newly formed in the matrix, and unresolved network type precipitates remained on the grain boundary. The network type precipitates and the granular and flake precipitates formed by heat treatment were confirmed to be ${\mu}$ phase intermetallic compounds with similar compositions. Due to the increase of the W content and the heat treatment, hardness and tensile strength were significantly increased. However, tensile strength after aging treatment was decreased with the W content. These results can be explained in that brittle fracturing by the unresolved network type precipitates dispersed in the grain boundary was predominant over ductile fracturing by the dimple ruptures originating from the fine granular precipitates in the matrix.

• Journal of Korean Society for Atmospheric Environment
• /
• 제18권E4호
• /
• pp.203-213
• /
• 2002

Receptor modeling is one of statistical methods to achieve reasonable air pollution strategies. In order to maintain and manage ambient air quality, it is necessary to identify sources and to apportion its sources for ambient particulate matters. The main purpose of the study was to survey seasonal trends of inorganic elements in the coarse and fine particles. Second, this study has attempted emission sources qualitatively by a receptor method, the PMF mo-del. After that. both PMF (positive matrix factorization) model and TTFA (target transformation factor analysis) model were applied to compare and to estimate mass contribution of coarse and fine particle sources at the receptor. A total of 138 sets of samples was collected from 1989 to 1996 by a low volume cascade impactor with 9 size fraction stages at Kyung Hee University in Korea. Sixteen chemical species (Si, Ca, Fe, K, Pb, Na, Zn, Mg, Ba, Ni, V, Mn, Cr, Br, Cu. Co) were characterized by XRF. The study result showed that the weighted arithmetic mean of coarse and fine particles were 51.3 and 54.4 $\mu\textrm{g}$/㎥, respectively. Contribution of both particle fractions were esti-mated using TTFA and PMF models. The number of estimated sources was seven according to TTFA model and 8 according to PMF model. Comparison of TTFA and PMF revealed that both methodologies exhibited similar trends in their contribution pattern. However, large differences between contributions were observed in some sour-ces. The results of this study may help to suggest control strategies in local countries where known source profiles do not exist.