Explore the vast range of titles available.

Rapid movement of the melt pool (at a speed around 1 m/s) in selective laser melting of metal powder directly implies rapid solidification. In this work, the length scale of the as-built microstructure of parts built with the alloy AlSi10Mg was measured and compared with the well-known relationship between cell size and cooling rate. Cooling rates during solidification were estimated using the Rosenthal equation. It was found that the solidification structure is the expected cellular combination of silicon with α-aluminum. The dependence of measured cell spacing on calculated cooling rate follows the well-established relationship for aluminum alloys. The implication is that cell spacing can be manipulated by changing the heat input. Microscopy of polished sections through particles of the metal powder used to build the parts showed that the particles have a dendritic-eutectic structure; the dendrite arm spacings in metal powder particles of different diameters were measured and also agree with literature correlations, showing the expected increase in secondary dendrite arm spacing with increasing particle diameter.

Heat treatment of Type 304 stainless steel in the range of 1273 K (1000 °C) to 1473 K (1200 °C) can transform manganese silicate inclusions to manganese chromite (spinel) inclusions. During heat treatment, Cr reacts with manganese silicate to form spinel. The transformation rate of inclusions depends strongly on both temperature [in the range of 1273 K to 1473 K (1000 °C to 1200 °C)] and inclusion size. A kinetic model, developed using FactSage macros, showed that these effects agree quantitatively with diffusion-controlled transformation. A simplified analytical model, which can be used for rapid calculations, predicts similar transformation kinetics, in agreement with the experimental observations.

The blast furnace (BF) process accounts for over 90% of global iron ore-based steel production and remains a major contributor to CO2 emissions. This study investigates the variability in operations across the global BF fleet and its impact on CO2 emissions. Using plant-level data from 2011 to 2021, we find that variation in the composition of inputs results in emissions ranging from 1.20 to 2.08 tons of CO2 per ton of hot metal (tCO2 tHM−1) globally, driven by differences in fuel and reductant consumption. Our estimates suggest global emissions could have been lower by 2.8%—and up to 9.6%—if each furnace operated at its historical or national minimum CO2 emissions intensity. We use furnace-level data to find even greater variation within and across individual furnaces at the national level, estimating potential for CO2 emissions reductions of 5.7%–15.5% in the United States. These findings suggest substantial latitude to incentivize plants to reduce CO2 emissions without new capital investment, by up to an estimated 1.35 billion tons of CO2 cumulatively across the global BF fleet from 2011–2021. It further underscores the limitations of relying on ‘best available technology’ or country-specific emissions factors in policy and planning efforts.

This work investigated the use of FactSage macros to simulate steel–slag and steel–inclusion reaction kinetics in silicon-manganese killed steels, and predict oxide inclusion composition changes during ladle treatment. These changes were assessed experimentally using an induction furnace to simulate deoxidation and slag addition. The average steel mass transfer coefficient for the experimental setup was calculated from the analyzed aluminum pick-up by steel. Average oxide inclusion composition was measured using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Confocal laser scanning microscopy was used to assess the physical state (solid or liquid) of oxide inclusions in selected samples. The changes in the chemical compositions of the oxide inclusions and the steel agreed with the FactSage macro simulations.

A product-scale part was additively manufactured from Inconel 718 by laser powder-bed fusion. The thermal and microstructural behavior was experimentally examined to reveal physical characteristics while a high fidelity numerical model was developed to predict characteristics throughout the part volume. Three physical characteristics were considered in the present study: (1) thermal evolution during the build, (2) melt pool configuration, and (3) the final microstructure as-deposited. Thermal simulations were performed by finite element calculation while the microstructure was predicted from the calculated thermal history and existing theoretical correlations. Predicted results were thoroughly confirmed through comparison with experimental measurements. Ultimately, the present work aims to illustrate the integration of the computational method as tools to provide manufacturing qualification for part production by AM.

Based on equilibrium considerations, copper sulfide is not expected to form in manganese-containing steel, yet previous workers reported finding copper sulfide in transmission electron microscope samples which had been prepared by electropolishing. It is proposed that copper sulfide can form during electrolytic dissolution because of the much greater stability of copper sulfide relative to manganese sulfide in contact with an electrolyte containing copper and manganese cations. This mechanism has been demonstrated with aluminum-killed steel samples.

In this study, an improved water-cooled copper probe was used to obtain solidified films of a mold flux used to cast peritectic steel. Different bulk temperatures of molten mold flux and different probe immersion times were used. The results reveal that the surface roughness of the slag film (in contact with the copper probe) has no direct relationship with solidification crystallization or devitrification in the slag film. Higher bulk temperatures (of molten flux) gave rougher surface slag-probe interfaces. Pores contribute to the surface roughness.

Iron ore pellets, reduced with hydrogen, were isothermally carburized in CH 4 -H 2 -N 2 at 823 K, 923 K, and 1023 K (550 °C, 650 °C, and 750 °C). Temperature strongly affected the total carbon concentration after carburization; significant unbound carbon deposited at the highest temperature. For the range of sizes tested (10 to 12 mm), pellet size did not affect carburization. The variability between pellets was much smaller than for industrial pellets; inhomogeneous gas distribution likely affects carburization under large-scale industrial conditions.

A higher-basicity mold flux (binary basicity 1.74) for peritectic grades showed similar solidification behavior to conventional high-basicity fluxes. Upon solidification of the mold flux onto a water-cooled copper probe, interfacial roughness at the copper-mold flux interface developed, while the film was glassy. Cuspidine was the major crystalline phase (as for conventional fluxes), but with a lathlike shape, containing some aluminum.

The nature of MgO and Al 2 O 3 dissolution in metallurgical slags may affect production cost, efficiency, and product quality. However, the rate-limiting dissolution mechanism, chemical reaction or boundary layer diffusion, is not well understood. In the present report, the dissolution mechanism of MgO and Al 2 O 3 in metallurgical slag was evaluated based on available literature data. The mass balance between the dissolving particle and the flux equation through the boundary layer was applied to predict the dissolution curve. The influence of fluid flow was taken into account to calculate the mass transfer rate at the oxide/slag interface. It was found that the rate-limiting step of MgO and Al 2 O 3 dissolution is the same: mass transfer through the boundary layer. Depending on the slag composition and experimental temperature, the effective diffusion coefficient for MgO and Al 2 O 3 dissolution falls in the range of 10 −12 to 10 −9  m 2 /s.