• Transactions of Materials Processing
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• v.19 no.5
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• pp.311-319
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• 2010

Rare earth metal Ce has a relatively low melting point and high specific gravity. Because of its significantly high affinity to oxygen, nitrogen and sulfur, it is highly usable as a steel refining agent. However, because Ce compound has relatively high specific gravity, it is difficult to be separated from molten steel through floatation, and it degrades the purity of molten steel, or may clog the nozzle in continuous casting. Such problem may be solved by using an appropriate deoxidation agent together with Ce and settling molten steel sufficiently after refining. Thus a fundamental study in the formation behavior of non-metallic inclusion in Ce added Hyper Duplex STS melts was investigated. The addition amount of Ce, melt temperature were considered as experimental variables. A main non-metallic inclusion in mother alloy is 51(wt%MnO) - 27.6(wt%SiO$_2$)- 10.9(wt%$Cr_2O_3$). Non-metallic inclusion was dramatically decreased and the particle size was fined as the amount of Ce increased. Moreover (%MnO) and (%SiO$_2$) of non-metallic inclusion were decreased. But (%$Al_2O_3$)were relatively increased. The number of non-metallic inclusion were decreased and the large particle size were increased by increasing the temperature of molten steel.

• Metals and materials international
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• v.24 no.6
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• pp.1394-1402
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• 2018

This study investigates the mechanism of MnS precipitation on $Al_2O_3-SiO_2$ inclusions during the solidification of non-oriented silicon steel, especially the influence of the phase structures and sizes of the oxides on the MnS precipitation, by scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectrometry. The investigation results show that MnS tends to nucleate on submicron-sized $Al_2O_3-SiO_2$ inclusions formed by interdendritic segregation and that it covers the oxides completely. In addition, MnS can precipitate on micron-sized oxides and its precipitation behavior is governed by the phase structure of the oxides. The MnS embryo formed in a MnO-containing oxide can act as a substrate for MnS precipitation, thus permitting further growth via diffusion of solute atoms from the matrix. MnS also precipitates in a MnO-free oxide by the heterogeneous nucleation mechanism. Furthermore, MnS is less prone to precipitation in the $Al_2O_3$-rich regions of the $Al_2O_3-SiO_2$ inclusions; this can be explained by the high lattice disregistry between MnS and $Al_2O_3$.

• Journal of Applied Reliability
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• v.15 no.3
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• pp.197-206
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• 2015

Failure analysis of pre-insulated pipe (SPPS 380, 400A) transporting high temperature water ($95{\sim}110^{\circ}C$) for a plant was carried out. The damaged area (${\Phi}5mm$) of pre-insulated pipe was found only on welds. The chemical composition of damaged pipe meets specification of carbon steel pipes for pressure service (KS D 3562). As results of microstructure analysis, crack propagated from outer to inside after pitting corrosion occurred on the outside surface. The non-metallic inclusion existed on the end of crack. And the non-metallic inclusion continuously and linearly formed along with the bond line of welds. Based on SEM-EDS analysis, the nonmetallic inclusions have higher Manganese (Mn) and Oxygen (O) content but sulfur (S) was not detected. As results of water quality analysis, hydrogen ion concentration and minerals like Fe, Mg, Si were in low level. But the content of dissolved oxygen (11.2 ppm) was slightly higher than that of standard. It seems that the cause of damaged pipe is grooving corrosion due to MnO inclusion formed on bond line and corrosion took place nearby welds.

• Metals and materials international
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• v.24 no.6
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• pp.1432-1437
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• 2018

This work investigated edge-cracking behavior of equiatomic CoCrFeMnNi high-entropy alloy during hot rolling at rolling temperatures $500{\leq}T_R{\leq}1000^{\circ}C$. Edge cracks did not form in the material rolled at $500^{\circ}C$, but widened and deepened into the inside of plate as $T_R$ increased from $500^{\circ}C$. Edge cracks were most severe in the material rolled at $1000^{\circ}C$. Mn-Cr-O type non-metallic inclusion and oxidation were identified as major factors that caused edge cracking. The inclusions near edge region acted as preferential sites for crack formation. Connection between inclusion cracks and surface cracks induced edge cracking. Rolling at $T_R{\geq}600^{\circ}C$ generated distinct inclusion cracks whereas they were not serious at $T_R=500^{\circ}C$, so noticeable edge cracks formed at $T_R{\geq}600^{\circ}C$. At $T_R=1000^{\circ}C$, significant oxidation occurred at the crack surface. This accelerated edge crack penetration by embrittling the crack tip, so severe edge cracking occurred at $T_R=1000^{\circ}C$.

• Economic and Environmental Geology
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• v.10 no.1
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• pp.1-18
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• 1977

Chongyang tungsten ore deposits, one of the most important tungsten mines in South Korea, me open space filling hydrothermal vein deposits embedded in Precambrian biotite gneiss and, Cretaceous (?) granite porphyry. Some wolframite-bearing quartz veins are closely associated with -quartz porphyries which strike about $N15^{\circ}-25^{\circ}W$ and dip $800^{\circ}SE$ to vertical. Mineralization took place in near vertical vein systems of 5 to 2000 meter long in the biotite gneiss and granite porphyry stock during early Cretaceous and Tertiary (?) period. The hydrothermal mineral paragensis has indicated that there were two major stages: vein and vug stages. The principal vein mineral is wolframite in a gangue of quartz with small amount of fluorite, pyrite, beryl and carbonate minerals. Present in minor amounts are molybdenite, bithmuthinite, native bismuth, arsenopyrite, galena, chalcopyrite, pyrrhotite, sphalerite and scheelite. Fluid inclusion study from the minerls at Chongyang mine reveals that vein stage fluids attained a temperature range of $200^{\circ}C-355^{\circ}C$ and vug stage $160^{\circ}C-350^{\circ}C$. The filling temperatures show the higher range of $200^{\circ}-355^{\circ}C$ in quartz and $280^{\circ}C-348^{\circ}C$ in beryls, whereas the lower emperature range of $283^{\circ}C-295^{\circ}C$ in rhodochrosite and $160^{\circ}-253^{\circ}C$ in fluorites. These temperatures are in reasonably good agreement with mineral paragnesis in this ore deposits. Volfamite minerals were analysed for major components. $WO_3$, MnO and FeO by wet chemical method. Chemical analysis indicates that they contain 70.56-71.54% $WO_3$, 8.52-10.01% MnO and 10.00-11.58% FeO. MnO/FeO ratios of wolframites shows the range of 0.78-0.94 which maybe indicates a comparatively high temperature type of hydrothermal deposits.

• Journal of the Mineralogical Society of Korea
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• v.17 no.4
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• pp.309-325
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• 2004

The Cannington Ag-Pb-Zn deposit, northwest Queensland, Australia developed around the host rocks composing banded and migmatitic gneisses, sillimanite-garnet schist and amphibolite. Three crystal habits of sillimanite, gahnite (Zn-spinel) and garnet porphyroblasts occurred on the host rocks of the Cannington deposit could be used to delineate metamorphism that closely associated with Zn-mineralization in the deposit. Linkages the metamorphism to Zinc-mineralization is determined in four chemical systems, KFMASH (K$_2$O-FeO-MgO-Al$_2$O$_3$-SiO$_2$-$H_2O$), KFMASHTO (K$_2$O-FeO-MgO-Al$_2$O$_3$-SiO$_2$-$H_2O$-TiO$_2$-Fe$_2$O$_3$), NCKFMASH (Na$_2$O-CaO-K$_2$O-FeO-MgO-AlO$_3$-SiO$_2$-$H_2O$) and MnNCK-FMASH (MnO-Na$_2$O-CaO-K$_2$O-FeO-MgO-AlO$_3$-SiO$_2$-$H_2O$), using THERMOCALC program (version 3.1; Powell and Holland 1988). Partial melting in MnNCKFMASH and NCKFMASH systems occurs at lower temperature than in the KFMASH and KFMASHTO systems. The partial melting temperature decreases with increasing of Na/(Na+Ca+K) of the bulk rock compositions in the MnNCKFMASH system. The host rocks have melted ca 15 vol.% in the MnNCKFMASH system at peak metamorphic conditions (634$\pm$62$^{\circ}C$ and 4.8$\pm$1.3 kbar), but partial melting have not occurred in KFMASHTO system. Based on calculations of sillimanite isograd in different systems and sillimanite modal pro-portion, prismatic and rhombic sillimanite and gahnite porphyroblasts including prismatic sillimanite inclusion probably have resulted from pressure and temperature increasing through partial melting (from 550～$600^{\circ}C$, 2.0～3.0 kbar to 700～75$0^{\circ}C$, 5.0～7.0 kbar), furthermore have experienced N-S then W-E crustal shortening during D$_1$ and D$_2$ deformation. Consequently, Zinc mineralization related to gahnite growth occurred during D$_2$ and was redistributed and upgraded by partial melting and retrograde metamorphism into structural and rheological sites during shearing in D$_3$.

• Korean Journal of Materials Research
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• v.16 no.9
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• pp.584-591
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• 2006

To enhance the machinability of the austenite stainless alloys, Mn and S were added to form MnS in the austenite matrix. Recently, Ca is also added to increase machinability. The alloying elements, such as C, Mn, S, Ca, and Al, are known to affect machinability, but those roles are not well understood. In this study, the ingots, controlled of alloying elements, C, Mn, S, Ca, Al, were prepared in the 304 stainless steel. The relationship between microstructure and machinability was compared to understand the role of alloying elements. It was proved that Mn and S enhanced machinability but C reduced it by analyzing cutting force on machining in the lathe. The alloying elements, Ca and Al, made a complex oxide compound of Mn-S-Ca-Al-Si-O, which results in increasing tool life. The ferrite volume fraction was changed with alloying elements and the effect of the ferrite fraction on machining was also discussed.

• Economic and Environmental Geology
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• v.12 no.4
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• pp.181-195
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• 1979

The Nambu orebodies of the Okbang tungsten mine are hosted in the Precambrian amphibolite and Weonnam formation. These orebodies can be classified into two types; The scheelite-bearing ore vein occurring in the amphibolite (the Nambu 1, 2 adits) and tungsten-bearing quartz vein along the contact between the amphibolite and the Weonnam formation (the Young-ho, -1, -2, -3 levels). The scheelite-bearing ore vein in the amphilbolite is discontinuous, narrow, and highly irregular in geometry, occurring only within the amphibolite with which of the vein is graduational. Based on these feature of the mode of occurrence, the origin of this ore type might be attributed to a potential segregation of tungsten ore fluid in situ from hornblenditic basic magma of the host rock. Tungsten-bearing quartz vein, however, is considered to have deposited along the N30-60E trending fractures as a later hypothermal vein after the hornblendite was emplaced. The principal ore mineral is scheelite with minor amount of wolframite, and the gangue minerals are quartz, and small amounts of fluorite, pyrrhotite, chalcopyrite and calcite. Fluid inclusion study of minerals from the Nambu orebody reveals that the fluids in fluorite of the scheelite-bearning ore vein attained a temperature range of $208{\sim}256^{\circ}C$ and those in quartz from the tungsten-bearing quartz vein a temperature range of $220{\sim}357^{\circ}C$. The real formation temperatures can be somewhat higher than filling temperatures, if pressure correction is made. Chemical analysis of 8 amphibolitc samples on major and some trace elements indicate that the amphibolite is igneous origin. On a Niggli diagram (al-alk)versus c, the analytical values are plotted on an igneous field, and on a Niggli diagram mg versus c they follow a karroo igneous trend line. According to the Ba, Cr, and Ni versus Niggli mg plots suggested by Leake (1964), Okbang amphibolite fall outside a pelitic field and compare favorably with his plots form ortho-amphibolites. Analitical values of $MoO_3$ of 8 samples of scheelite minerals from the Nambu orebody indicate that the tungsten-bearing quartz vein (type n) of Nambu orebody shows a range from 1. 69% to 4.38% which is higher than 0.94%~3.25% $MoO_3$ for the scheelite-bearing ore vein (type I). This fact indicates that the type II was deposited in a lower $fO_2/higher$ $fO_2$ environment and under lower temperature than the type I. Analysis of major components $WO_3$, MnO, and FeO of 6 samples of wolframite from the type II veins revealed that they contain 73.35~76.2% $WO_3$, 7.94~11.63% MnO, and 10.53~14.82% FeO. MnO/FeO ratios of wolframite shows the range of 0.85~1.17 which suggests a slightly higher temperature type of deposits than other major tungsten deposits in the country.

• Journal of Conservation Science
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• v.29 no.4
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• pp.367-378
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• 2013

Microstructures and nonmetallic inclusions of five forged iron axes and one cast iron axe were analyzed. The axes were excavated from the Proto-Three Kingdom Period site located in Yangchon, Gimpo. The forging objects were made of almost pure iron and low carbon steel, and only one among five were quenched after its figuration. Malleable cast iron structures showing on the casting suggest that the decarbonized casting method were applied. According to the results of nonmetallic inclusion analysis, the axes were produced by hammering the iron bloom which was attained with low-temperature -solid-reduction-method. Showing higher Fe content over $SiO_2$, it is assumed that the re-collecting rate of Fe was low because of the insufficient forging temperature and the impurities were included during the smelting process. It is assumed that the lime was used as a preparation because of detecting high Ca contents.

• Journal of the Korean Ceramic Society
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• v.21 no.2
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• pp.149-155
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• 1984

The effect of $ZrO_2$ dispersed phase on the mechanical properties in $Al_2O_3$-$ZrO_2$system has been studied. There are both metastable tetragonal phase and stable monoclinic phase of $ZrO_2$particles diespersed in Al2O3 matrix at room temperature. Metastable tetragonal $ZrO_2$ changes to the stable monoclinic structure within the stress field of the crack. And microcracks are formed by the expansion of $ZrO_2$during the tetragonal-monoclinic transformation on cooling. Therefore stress-induced phase transformation and inclusion-induced microcracking contribute to the mec-hanical properties of $Al_2O_3$-$ZrO_2$system. Sintered composites containing 10m/o $ZrO_2$ yield KiC values of 6.5MN/$m^{3/2}$ much greater than that of pure $Al_2O_3$ This increase results from microcrack extension and stress-induced phase transformation absor-bing energy by crack propagation. Flexural strength of composites is decreased considerably in comparison with pure $Al_2O_3$ This decrease results from microcrack as a crack former and higher porosity than pure $Al_2O_3$.