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Kawasaki, Japan

The sampling of raw materials in the rotary kiln, firing experiment by the experimental kiln, and water quenching experiment have been performed, and the clarification of behavior of the reduction and the growth of metal has been attempted by SEM-EDS. In the amorphous serpentine region, NiO has very high reducibility than FeO. The increase in heating temperature above 1 273 K allows the fine reduced metal to be confined in the silicate, which causes the extraction by the bromine methyl alcoholic solution to be difficult. This allows the degree of reduction to enter apparently the depression region. However, the increase in heating temperature above 1 525 K allows melt to occur, which causes the fine metal to coalesce with each other. Therefore, the degree of reduction leaves the depression region, and approaches the equilibrium values. Low-MgO and high-FeO NiO silicate is enriched by the fractional crystallization, and thereafter reduction reaction is enhanced. From the result of SEM observation that metals occur from the lower temperature in the low-MgO and high-FeO ore containing much point defect, NiO and FeO in the crystal lattice are reduced via cationic and electronic defect species, the oxygen occurred diffuses toward the crystal surface via vacancies. However, the lack of experimental data of defect chemistry in Ni-ore requires the further investigation. From the fact that the temperature of the melt occurrence coincides with the temperature of metal beginning to grow largely in SEM observation, it is confirmed that the fine metals coalesce with each other via melt to grow. © 2012 ISIJ. Source

The investigation of influence of non-stoichiometric serpentine in saprolite Ni-ore on a softening behavior of raw materials has been successfully carried out by SEM-EDS analysis. Serpentine in ore is classified into the low-MgO and high-FeO, high-MgO and low-FeO type. The ratio of that depends on the degree of leaching of MgO during the weathering. The crystal lattice of serpentine is significantly disturbed by the leaching of MgO, and has cation component much lower than stoichiometric composition, which allows replacement of much Mg 2+ by Fe 3+ to be enhanced during weathering. This leads to the formation of nonstoichiometric low-MgO type serpentine with much Fe 2O 3. The recrystallization of that continually takes place in accordance with equilibrium. Therefore, it is not until 1 300°C that olivine (2(Mg 1-xFe x)·SiO 2) occurs, in that case, low-MgO and high-SiO 2-FeO amorphous silicate is simultaneously formed as the residual melt. Further, CaO in flux and Al 2O 3 in spinel melt into that melt, which allows melting temperature of melt to be still more reduced. In the recrystallization of non-stoichiometric high-MgO type of serpentine, olivine occurs from around 900°C. High-MgO-SiO 2 and low-FeO amorphous silicate is simultaneously formed as the residual of recrystallization. Whereas, the contents of higher-MgO and lower-FeO than Ore-A leads to difficulty in melt generation. Thus, melt generation in saprolite Ni-ore occurs as the residual in the recrystallization (i.e., formation of olivine) of non-stoichiometric serpentine, being enhanced by the amount of MgO leached and Fe 3+ by which Mg 2+ is emplaced in the weathering. © 2012 ISIJ. Source

Park J.H.,University of Ulsan | Todoroki H.,Nippon Yakin Kogyo Co.
ISIJ International

The latest publications regarding the development of technology to control inclusion compositions focusing on MgO . Al2O3 spinel inclusions were summarized in this review article. The problems caused by spinel inclusions, which affect practice as well as products were shown. The formation mechanism of MgO . Al2O3 spinel inclusions is secondly explained thermodynamically from the view points of chemistries of molten steels and slag compositions. Furthermore, crystallization behaviour of spinel was introduced. Countermeasures conducted in practices and laboratories were shown along with some problems still left that should be solved in the future. © 2010 ISIJ. Source

Nippon Yakin Kogyo Co. | Date: 2010-02-26

As a stainless steel for a metal part for clothing ornament capable of working into a complicated form part and having such nonmagnetic properties that the worked part can cope with the detection through needle detecting device is provided a high-Mn austenitic stainless steel having a chemical composition comprising C: 0.02-0.12 mass %, Si: 0.05-1.5 mass %, Mn: 10.0-22.0 mass %, S: not more than 0.03 mass %, Ni: 4.0-12.0 mass %, Cr: 14.0-25.0 mass % and N: 0.07-0.17 mass %, provided that these components are contained so that cal (mass %) represented by the following equation (1) is not more than 5.5 mass %: and having a magnetic permeability of not more than 1.003 under a magnetic field of 200 kA/m.

A boron-containing stainless steel having excellent hot workability and weldability and a good surface quality is proposed and is a boron-containing stainless steel comprising C: 0.0010.15 mass %, Si: 0.12 mass %, Mn: 0.12 mass %, Ni: 525 mass %, Cr: 1127 mass %, B: 0.052.5 mass %, Al: 0.0050.2 mass %, O: 0.00010.01 mass %, N: 0.0010.1 mass %, S: not more than 0.005 mass %, one or both of Mg: 0.00010.005 mass % and Ca: 0.00010.005 mass % and the remainder being Fe and inevitable impurities provided that a part of Si, Al, Mg, Ca and S is included as a non-metallic inclusion made of sulfide and/or oxysulfide.

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