KAGRA is a 3-km interferometric gravitational wave telescope located in the Kamioka mine in Japan. It is the first km-class gravitational wave telescope constructed underground to reduce seismic ...noise, and the first km-class telescope to use cryogenic cooling of test masses to reduce thermal noise. The construction of the infrastructure to house the interferometer in the tunnel, and the initial phase operation of the interferometer with a simple 3-km Michelson configuration have been completed. The first cryogenic operation is expected in 2018, and the observing runs with a full interferometer are expected in 2020s. The basic interferometer configuration and the current status of KAGRA are described.
Attack on Magnesia Crucible by Molten Iron Dan, Takehiro; Aritomi, Noriyoshi; Ogawa, Kzusyukii ...
Journal of the Japan Institute of Metals and Materials,
1992, 19920101, Volume:
56, Issue:
1
Journal Article
Peer reviewed
Open access
The purpose of this research is to elucidate an interaction mechanism at an interface between molten iron and magnesia crucible. Pure iron used in the present study has less content of impurities ...except for oxygen, the content of which is classified into two groupes (15 and 400 mass ppm). Magnesia crucible is commercial dense product. Iron specimen has been molten for 10∼60min at 1600°C under Ar atmosphere in a tungsten mesh-heater furnace. After cooling, the specimen is treated and observed with optical and scanning electron microscopes and a surface roughness detector. And then the specimen interface is analysed with an X-ray probe microanalyser and an analytical electron microscope and identified with an X-ray diffractometer. The results obtained are as fellows: (1) Depending on the initial oxygen content in iron specimens, the appearance of the interface between the iron specimen and the magnesia crucible was very different. In the case of low oxygen content (15 mass ppm) in molten iron, the interface of magnesia crucible after melting was the almost same as that before melting except for the very slight corrosion at the grain boundary. On the contrary, the magnesia crucible was extraordinarily attacked by molten iron which had a high oxygen content (400 mass ppm). (2) Oxygen in molten iron is very interface-active. The dissolved oxygen concentrates on the interface of molten iron and crucible, and forms a single molecular FeO layer at the interface in the case of 400 mass ppm O. On the otherhand, no layer is formed in the case of 15 mass ppm O. (3) Accordingly, in the former case there may be an oxide phase-oxide phase contact at the interface. The latter interface consists of metal and oxide phases. It is considered that such different combinations cause the different types of attack on the magnesia crucible by molten iron.
In order to study the formation processes of deoxidation products with manganese during the solidification of iron, inclusions in iron ingots, which were deoxidized with 2% manganese or with 0.2% ...silicon--2% manganese in an alumina crucible and solidified unidirectionally, were investigated. Almost all the deoxidation products in all the ingots deoxidized with both kinds of deoxidizers, were of nearly spherical shape, and usually contained aluminum and silicon besides manganese, oxygen and sulfur. The oxygen content of the ingot did not vary significantly with the kind of the above two deoxidizers. From such experimental results and the estimation of the supersaturation for the formation of some kinds of deoxidation products, it was considered that the deoxidation products with manganese during the solidification of iron in the alumina crucible had nucleated as MnO. Al sub 2 O sub 3 (s) and grown in liquid state, reacting eith wn, Si, S and O. 20 ref.--AA
The purpose of the present work is to investigate the contamination of molten iron with crucible materials during the melting process. High purity iron was melted at 1873 K for 900 s in an alumina ...crucible by use of a tungstenmesh heater furnace, and the ingot was subjected to the chemical analysis. The cross section of the ingot was deeply etched electrolytically and was observed with a scanning electron microscope. From the deeply etched cross section, inclusions were extracted onto a carbon film ancl the chemical composition was analyzed with an analytical electron microscope. The results are as follows: (1) Iron was contaminated with silicon during the melting process. The extent of the contamination depended on the silica content of the crucible. (2) By use of an alumina crucible which contains silica by only 0.005 mass%, the contamination of melt was suppressed. (3) The silicon content of inclusions depended on both the silicon and oxygen contents of ingots. It can be estimated by the equilibrium relationship and the change in melt composition during solidification.
In order to study the formation processes of deoxidation products with manganese during the solidification of iron, inclusions in iron ingots, which were deoxidized with 2% manganese or with 0.2% ...silicon-2% manganese in an alumina crucible and solidified unidirectionally, were investigated. Almost all the deoxidation products in all the ingots deoxidized with both kinds of deoxidizers, were of nearly spherical shape, and usually contained aluminum and silicon besides manganese, oxygen and sulfur. The oxygen content of the ingot did not vary significantly with the kind of the above two deoxidizers. From such experimental results and the estimation of the supersaturation for the formation of some kinds of deoxidation products, it was considered that the deoxidation products with manganese during the solidification of iron in the alumina crucible had nucleated as MnO•Al2O3(s) and grown in liquid state, reacting with Mn, Si, S and O.
For the purpose of obtaining some preliminary information on the formation of deoxidation products with Al during the solidification of Fe, the morphology, composition and distribution of inclusions ...in Fe ingots, which were deoxidized with 0.1 or 2 mass% of Al in a stirred melt and solidified unidirectionally, were investigated with special attention to the confirmation of alumina inclusions of the low-temperature types. Relatively large inclusions in the core region of both kinds of ingots were mainly of α-Al2O3, but inclusions of SiO2, iron sulphide, or iron oxide containing Al and/or Si and/or S, and/or other elements were also found. These inclusions were preferentially located in or around a characteristic etched figure of matrix. Fine miscellaneous inclusions less than 0.1 μm, perhaps formed in the solidified matrix, also existed. AlN inclusions with characteristic shapes were observed throughout the ingot deoxidized with 2 mass% Al. In the top region of this kind of ingot, fine inclusions with a characteristic shape and having a crystallographic structure, were densely located. From such inclusions, Al and S were mainly detected. Alumina inclusions of the low-temperature types were not confirmed in all the ingots in this study. Formation processes of iron aluminate and AlN inclusions during solidification were discussed.
Attack on Magnesia Crucible by Molten Iron Dan, Takehiro; Aritomi, Noriyoshi; Ogawa, Kazuyuki ...
Materials Transactions, JIM,
1993, Volume:
34, Issue:
5
Journal Article
Open access
The purpose of this research is to elucidate an interaction mechanism at an interface between molten iron and the magnesia crucible. Pure iron used in the present study had less content of impurities ...except for oxygen, the content of which was classified into two groups (15 and 400 mass ppm). Magnesia crucibles were commercial dense products. Iron specimen was molten for 10∼60 min at 1600°C under Ar atmosphere in a tungsten mesh-heater furnace. After cooling, the specimen was treated and observed with optical and scanning electron microscopes. And then the specimen interface was analyzed with an electron probe micro-analyzer, an analytical electron microscope and a surface roughness measuring instrument. It was also identified with an X-ray diffractometer. The results obtained are as follows: (1) Depending on the initial oxygen content in the iron specimen, the appearance of the iron specimen-magnesia crucible interface was very different. In the case of a low oxygen content (15 mass ppm) in molten iron, the interface of the magnesia crucible after melting was almost the same as that before melting except for the very slight corrosion at the grain boundary. On the contrary, the magnesia crucible was extraordinarily attacked by molten iron which had a high oxygen content (400 mass ppm). (2) In the latter case, the solidus temperature of the MgO–FeO phase formed at the interface of the magnesia crucible with molten iron lowers to about 2600°C. Although it is still solid at the experimental temperature, the surface rearrangement among the relevant phases may occur. (3) Oxygen in molten iron is very interface-active. The dissolved oxygen atoms are concentrated on the interface between molten iron and the crucible, and form FeO monolayer at the iron interface in the case of 400 mass ppm O. On the other hand, no FeO layer is formed in the case of 15 mass ppm O. It is considered that such a monolayer may cause different types of attack on the magnesia crucible by molten iron.
The purpose of the present work is to investigate the contamination of molten iron with crucible materials during the melting process. High purity iron was melted at 1873 K for 900 s in an alumina ...crucible by use of a tungsten-mesh heater furnace, and the ingot was sectioned for chemical analysis. The cross section of the ingot was deep-etched electrolytically and was observed with a scanning electron microscope. From the deep-etched cross section, inclusions were extracted onto a carbon film and their chemical composition was determined with an analytical electron microscope. The results are as follows: (1) Iron was contaminated with silicon during the melting process. The silicon content of the iron in-got depended on the silica content of the crucible. (2) By use of an alumina crucible which contained less amount of silica, 0.005 mass%, the silicon contamination of melt was suppressed. (3) The silicon content of inclusions depended on both the silicon and oxygen contents of ingots. It can be estimated by both the postulated equilibria which were obtained in terms of Turpin and Elliott’s treatment and the change in melt composition during solidification. (4) The composition of inclusions can be also presumed from a predicted Fe–Si–O system phase diagram.
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