The Penetration Behavior of an Annular Gas–Solid Jet Impinging on a Liquid Bath: The Effects of the Density and Size of Solid Particles

Top-blow injection of a gas?Csolid jet through a circular lance is used in the Mitsubishi Continuous Smelting Process. One problem associated with this injection is the severe erosion of the hearth refractory below the lances. A new configuration of the lance to form an annular gas?Csolid jet rather than the circular jet was designed in this laboratory. With this new configuration, the solid particles fed through the center tube leave the lance at a much lower velocity than the gas, and the penetration behavior of the jet is significantly different from that with a circular lance where the solid particles leave the lance at the same high velocity as the gas. In previous cold-model investigations in this laboratory, the effects of the gas velocity, particle feed rate, lance height of the annular lance, and the cross-sectional area of the gas jet were studied and compared with the circular lance. This study examined the effect of the density and size of the solid particles on the penetration behavior of the annular gas?Csolid jet, which yielded some unexpected results. The variation in the penetration depth with the density of the solid particles at the same mass feed rate was opposite for the circular lance and the annular lance. In the case of the circular lance, the penetration depth became shallower as the density of the solid particles increased; on the contrary, for the annular lance, the penetration depth became deeper with the increasing density of particles. However, at the same volumetric feed rate of the particles, the density effect was small for the circular lance, but for the annular lance, the jets with higher density particles penetrated more deeply. The variation in the penetration depth with the particle diameter was also different for the circular and the annular lances. With the circular lance, the penetration depth became deeper as the particle size decreased for all the feed rates, but with the annular lance, the effect of the particle size was small. The overall results including the previous work indicated that the penetration behavior of an annular jet is much less sensitive to the variations in operating variables than that of a circular jet. Correlation equations for the penetration depth that show good agreements with the measured values have been developed.     

Gas–Liquid Reduction Behavior of Hematite Ore Fines in a Flash Reduction Process

Metallurgical and Materials Transactions B - Novel ironmaking technologies that directly use the raw materials of iron ore fines without preprocessing have greater benefits in environmental...     

Gas–Solid Interactions During Nonisothermal Heat Treatment of a High-Strength CrMnCN Austenitic Steel Powder: Influence of Atmospheric Conditions and Heating Rate on the Densification Behavior

This work deals with gas?Csolid interactions between a high-alloyed steel powder and the surrounding atmosphere during continuous heating. It is motivated by the recently developed corrosion-resistant CrMnCN austenitic cast steels. Here, powder metallurgical processing would be desirable to manufacture highly homogeneous parts and/or novel corrosion-resistant metal-matrix composites. However, the successful use of this new production route calls for a comprehensive investigation of interactions between the sintering atmosphere and the metallic powder to prevent undesirable changes to the chemical composition, e.g., degassing of nitrogen or evaporation of manganese. In this study, dilatometric measurements combined with residual gas analysis, high-temperature X-ray diffraction (XRD) measurements, and thermodynamic equilibrium calculations provided detailed information about the influence of different atmospheric conditions on the microstructure, constitution, and densification behavior of a gas-atomized CrMnCN steel powder during continuous heating. Intensive desorption of nitrogen led to the conclusion that a vacuum atmosphere is not suitable for powder metallurgical (PM) processing. Exposure to an N₂-containing atmosphere resulted in the formation of nitrides and lattice expansion. Experimental findings have shown that the N content can be controlled by the nitrogen partial pressure. Furthermore, the reduction of surface oxides because of a carbothermal reaction at elevated temperatures and the resulting enhancement of the powder??s densification behavior are discussed in this work.     

Mathematical Analysis of the Solidification Behavior of Plain Steel Based on Solute- and Heat-Transfer Equations in the Liquid–Solid Zone

An analytical approximate solution to non-linear solute- and heat-transfer equations in the unsteady-state mushy zone of Fe-C plain steel has been obtained, assuming a linear relationship between the solid fraction and the temperature of the mushy zone. The heat transfer equations for both the solid and liquid zone along with the boundary conditions have been linked with the equations to solve the whole equations. The model predictions (e.g., the solidification constants and the effective partition ratio) agree with the generally accepted values and with a separately performed numerical analysis. The solidus temperature predicted by the model is in the intermediate range of the reported formulas. The model and Neuman’s solution are consistent in the low carbon range. A conventional numerical heat analysis (i.e., an equivalent specific heat method using the solidus temperature predicted by the model) is consistent with the model predictions for Fe-C plain steels. The model presented herein simplifies the computations to solve the solute- and heat-transfer simultaneous equations while searching for a solidus temperature as a part of the solution. Thus, this model can reduce the complexity of analyses considering the heat- and solute-transfer phenomena in the mushy zone.     

The Effect of Precipitation Characteristics on Hardening Behavior in Cu–Cr–Sn Alloy with Sn Variation

Powder Metallurgy and Metal Ceramics - The influence of minor solute additions of Sn on hardening behavior and microstructure evolution of the Cu–Cr–Sn alloys has been investigated with...     

The Possibility of Dense Materials Based on Obtaining an AlN–SiC Solid Solution by Self-Propagating High-Temperature Synthesis Gasostating

Russian Journal of Non-Ferrous Metals - The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis...     

The Influence of Hydrogen Concentration in an Ar–H2 Mixture on the Electrical Properties of Solid Oxide Fuel Cells

Powder Metallurgy and Metal Ceramics - Fuel cells are today among the most efficient and environmentally friendly devices for the production of electricity. They are developing rapidly and are...     

The Effect of Cold Rolling on Microstructure and Mechanical Properties of a New Cr–Mn Austenitic Stainless Steel in Comparison with AISI 316 Stainless Steel

In the present study the effect of room temperature rolling on microstructure and mechanical properties of a new Cr–Mn austenitic stainless steel (containing 12 %Cr, 23 %Mn and 0.13 %C) and AISI 316 steel was investigated. The specimens of these steels were cold rolled at various thickness reductions of 0, 12, 25, 37 and 50 %. Microstructural investigations were carried out using optical microscopy, magnetic field test and X-ray diffraction technique. Hardness and tensile test methods were also done to evaluate the mechanical properties. Results showed that some of austenite phase transformed to martensite during cold rolling in the 316 steel, while there was no strain induced transformation in the Cr–Mn steel. It was also found that the newly developed steel had higher strength and higher specific strength than those of the 316 steel, while its ductility was the same as that of the 316.     

The ontogeny of an idea: John Bowlby and contemporaries on mother–child separation.

In this contribution, the authors situate the development of Bowlby’s attachment theory against the background of the social, cultural, and scientific developments in interbellum Britain. It is shown that fairly early in his life Bowlby adopted one fundamental idea—that an infant primarily needs a warm and loving mother, and that separations from the mother are potentially damaging—and never substantially changed that basic notion in later years. Bowlby’s first and foremost goal—and his lifelong undertaking—was to convince certain others (e.g., orthodox psychoanalysts, psychiatrists, clinicians, and medical doctors) of the importance of this idea by theorizing and gathering empirical evidence. Bowlby’s view of mother love deprivation as the main source of maladjusted behavior was at variance with the views of many practitioners and theorists, but it was by no means fully novel and original. The authors show that Bowlby took inspiration from various persons and groups in British society with whom he shared basically similar views. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of self-efficacy on stressor–strain relations: Coping style as an explanatory mechanism.

The present study was designed to examine whether coping style influences the impact of self-efficacy on stressor–strain relations. It was hypothesized that high self-efficacy would weaken stressor–strain relations when accompanied by frequent use of active coping and infrequent use of avoidance coping. Data collected from 2,293 members of the U.S. Army revealed 3-way interactions among self-efficacy, role clarity, and active coping and among self-efficacy, work overload, and avoidance coping. As predicted, self-efficacy mitigated the effects of low role clarity on strain only when active coping was high. Also as expected, strain levels were lower for participants with high self-efficacy than for participants with lower self-efficacy when work overload was low but avoidance coping was high. Implications of these findings for occupational stress research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The unique effect of paternal depressive symptoms on adolescent functioning: Associations with gender and father–adolescent relationship closeness.

Prospective, longitudinal data from a community sample of 451 families were used to assess the unique contribution of paternal depressive symptoms to adolescent functioning. Results indicated that paternal depressive symptoms were significantly related to subsequent depressive symptoms in adolescent offspring; this association remained significant after controlling for previous adolescent depressive symptoms, maternal depressive symptoms, gender, and family demographic variables. Adolescent gender and perception of father–adolescent relationship closeness moderated this association such that paternal depressive symptoms were positively associated with adolescent depressive symptoms for girls whose relations with fathers lacked closeness. These findings add to a growing literature on the interpersonal mechanisms through which depression runs in families, highlighting the need for future investigation of paternal mental health, adolescent gender, and intrafamily relationship quality in relation to adolescent development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)