Formation and Evolution of DS-Type Inclusions in 15-5PH Stainless Steel

15-5PH stainless steel castings are key components in fracturing trucks. However, DS-type inclusions can lead to fatigue failure of the material. To elucidate the formation mechanism of large-size DS-type inclusions, the evolution, growth, and aggregation of inclusions during vacuum oxygen decarburization, ladle refining, and vacuum casting were studied. The results show that the DS-type inclusions with sizes larger than 20 μm were CaO–Al2O3–SiO2–MgO–CaS composite inclusions. After Si–Al additions in vacuum degassing, typical inclusions were spinel or Al2O3. After Ca–Si additions during ladle treatment, typical inclusions were liquid or dual-phase Al2O3–CaO–SiO2–MgO. During the solidification process, due to the segregation of S and the decrease in solubility, the typical inclusions in the final casting became Al2O3–CaO–SiO2–MgO–CaS. For optimal fatigue performance of stainless steel castings, slag and refractory composition control were also necessary because the [Mg] contents mainly come from the slag and lining.

Host-star and exoplanet compositions: a pilot study using a wide binary with a polluted white dwarf

ABSTRACT Planets and stars ultimately form out of the collapse of the same cloud of gas. Whilst planets, and planetary bodies, readily loose volatiles, a common hypothesis is that they retain the same refractory composition as their host star. This is true within the Solar system. The refractory composition of chondritic meteorites, Earth, and other rocky planetary bodies are consistent with solar, within the observational errors. This work aims to investigate whether this hypothesis holds for exoplanetary systems. If true, the internal structure of observed rocky exoplanets can be better constrained using their host star abundances. In this paper, we analyse the abundances of the K-dwarf, G200-40, and compare them to its polluted white dwarf companion, WD 1425+540. The white dwarf has accreted planetary material, most probably a Kuiper belt-like object, from an outer planetary system surviving the star’s evolution to the white dwarf phase. Given that binary pairs are chemically homogeneous, we use the binary companion, G200-40, as a proxy for the composition of the progenitor to WD 1425+540. We show that the elemental abundances of the companion star and the planetary material accreted by WD 1425+540 are consistent with the hypothesis that planet and host-stars have the same true abundances, taking into account the observational errors.

Processing of Nano Carbon Containing Low Carbon MgO-C Refractory : Effect of Mixing Route

Nano carbon, being finer in size, is difficult to mix uniformly in a refractory composition to achieve the advantages of nano-metric size and its associated properties. Development of N220 nano carbon containing MgO-C refractory has been studied by using three different mixing and processing routes. The developed products of different processing routes are compared by evaluation of the developed properties against the conventional 16 wt% graphite containing commercial MgO-C refractory composition. Nano carbon containing composition with optimized processing route is further characterized for phase analysis; microstructural studies; elemental distribution of carbon; thermal shock resistance, and pore size distribution and also compared against the conventional composition. batch prepared by the optimum processing route were further studied for measured by oil bath quenching method and thermal cycle method.

Recovery of Copper from Leached Tailing Solutions by Biosorption

Due to the progressive fall of the ore grades and the increasingly refractory composition of minerals, concentrating plants have increased which has led to an increase in the generation of tailings. Tailings, especially those obtained in the past, have remaining copper and other valuable species in quantities that can potentially be recovered, such as gold, silver, vanadium, and rare earth elements which transforms this abundant waste into a potential source of precious or strategic metals for secondary mining. One of the techniques of solid–liquid separation that processes solutions with low concentrations of metals corresponds to adsorption, and more recently biosorption, which is based on the use of biological matrices that do not constitute an environmental liability after application. Biosorption occurs as a consequence of the wide variety of active functional groups present in different types of biomass. Bacterial, fungal, plant, and algal biomasses have been described as biosorbents, mainly for the treatment of diluted and simple solutions. This work aims to recover copper from leached tailings using biomass of the red algae Gracilaria chilensis as a biosorbent. The tailing samples were taken from an abandoned deposit, in the north of Chile, and after an acid leaching copper was biosorbed, kinetics of adsorption and the equilibrium isotherms were studied, applying the Freundlich and Langmuir models. Operational parameters such as adsorbent dose, pH, and initial metal concentration were studied.

Recovery of Copper from Leached-Tailing Solutions by Biosorption

Mining is one of the main economic activities of several developing countries as Chile. Due to the progressive fall of the ore grades and the increasingly refractory composition of minerals, concentrating plants have increased that has led to an increase in the generation of tailings. Tailings, especially those obtained in the past, have remaining copper and other valuable species in quantities that can potentially be recovered, such as gold, silver, vanadium and rare earth elements. This transforms this abundant waste into a potential source of precious or strategic metals for secondary mining. One of the techniques of solid-liquid separation that allows the processing of solutions with low concentrations of metals corresponds to the adsorption, and more recently the biosorption, which is based on the use of biological matrices that do not constitute an environmental liability after application. Biosorption occurs as a consequence of the wide variety of active functional groups present in the different types of biomass. Bacterial, fungal, plant and algal biomasses have been described as biosorbents, mainly for the treatment of diluted and simple solutions. This work aims to recover copper from leached tailings using biomass of the red algae Gracilaria chilensis as a biosorbent. The tailing samples were taken from an abandoned deposit in the north of Chile and after an acid leaching copper was biosorbed, for which the kinetics of adsorption and the equilibrium isotherms were studied, applying the Freundlich and Langmuir models. Operational parameters such as adsorbent dose, pH and initial metal concentration were studied.

Differences in the Mechanical Properties of Lightweight Refractory Cementitious Composites Reinforced by Various Types of Fibers

Development of new composite materials is the worldwide extremely progressive branch of engineering activity. Composite materials are applied in many industries. The principle of composite materials is a combination of different materials providing an entirely new material with specific properties. Fiber-reinforced composites rank to the most frequently used composites because of their suitable mechanical properties. There were studied mechanical properties of fibre reinforced cementitious composites (FRCC) exposed to high temperatures of 600 °C and 1000 °C in the paper. For the production of refractory FRCC were used aluminous cement Secar®71 with 70 % of Al2O3. Various composites differed in the used type of fibers - basalt, carbon and ceramic fibres were applied in doses of 2 % by volume. For the experimental program were prepared prismatic specimens with the total dimensions of 40 × 40 × 160 mm3 and cured for 28 days in humid environment. Residual bulk density, flexural and compressive strength were investigated in the performed experimental program. The results showed the positive effect of the fibers used in refractory composition and the dependence on the length of the used fibers.