MICROSTRUCTURAL AND PHYSICOCHEMICAL PROPERTIES OF SOME ALUMINUM COOKING TOOLS OBTAINED BY ARTISANAL RECYCLING

Recycling metals waste is one of the ways to recover this waste, but also to preserve mining resources and fight against pollution. Aluminum is one of the most recycled metals due to its relatively low melting temperature, high conductivity, ductility, malleability and its high resistance to corrosion. In Togo, as in many West African countries, aluminum wastes are collected, melted and molded in artisanal way to make new objects for domestic use. The aim of this work is to investigate the process of artisanal aluminum recycling and use several modern techniques of characterization in order to improve thereafter products and manufacturing process. Two types of samples were subjected to a series of physicochemical analysis. One from an old aluminum pot (sample (a)) and the other cut from newly pot obtained after artisanal manufacturing (sample (b)). The measurement of the temperature inside the crucible during scarp aluminum melting operation reveals three temperatures ranges with a melting point around 750℃. Atomic absorption spectrometry (AAS) indicates that the two samples contain mostly aluminum, zinc, copper, magnesium and some traces of lead. Optical microscopy observations show that the alpha aluminum matrix was the most abundant phase with 80 to 90% of the observed area and some inclusions randomly dispersed. X- ray diffraction (XRD) confirms the presence of lines characteristic of alpha aluminum and bohemite (γ-AlOOH).

TECHNOGENIC IMPACT OF RADIOACTIVE CONTAMINATION OF METAL SMELTING PRODUCTS ON ENVIRONMENT AND POPULATION

The analysis of the distribution of radionuclides in the products of blast furnace and steelmaking melting operation processes is carried out. It was shown that the blast furnace melting process is considerably affected by natural radionuclides whereas steelmaking furnace process - by technogenic ones. The main impact on the environment is exerted by the gas-dust fraction, which contaminates the surrounding soil, vegetation and ground water during the settling process. An additional dose of external irradiation of the population and personnel is created by slag and metal fractions. High radiation doses are possible in case of ingestion of high-intensity sources of 60Co and 137Cs into the melt. Internal irradiation of people occurs due to gas and dust emissions.

Micro-Macro Relationship between Microstructure, Porosity, Mechanical Properties, and Build Mode Parameters of a Selective-Electron-Beam-Melted Ti-6Al-4V Alloy

The performance of two selective electron beam melting operation modes, namely the manual mode and the automatic ‘build theme mode’, have been investigated for the case of a Ti-6Al-4V alloy (45–105 μm average particle size of the powder) in terms of porosity, microstructure, and mechanical properties. The two operation modes produced notable differences in terms of build quality (porosity), microstructure, and properties over the sample thickness. The number and the average size of the pores were measured using a light microscope over the entire build height. A density measurement provided a quantitative index of the global porosity throughout the builds. The selective-electron-beam-melted microstructure was mainly composed of a columnar prior β-grain structure, delineated by α-phase boundaries, oriented along the build direction. A nearly equilibrium α + β mixture structure, formed from the original β-phase, arranged inside the prior β-grains as an α-colony or α-basket weave pattern, whereas the β-phase enveloped α-lamellae. The microstructure was finer with increasing distance from the build plate regardless of the selected build mode. Optical measurements of the α-plate width showed that it varied as the distance from the build plate varied. This microstructure parameter was correlated at the sample core with the mechanical properties measured by means of a macro-instrumented indentation test, thereby confirming Hall-Petch law behavior for strength at a local scale for the various process conditions. The tensile properties, while attesting to the mechanical performance of the builds over a macro scale, also validated the indentation property measurement at the core of the samples. Thus, a direct correlation between the process parameters, microstructure, porosity, and mechanical properties was established at the micro and macro scales. The macro-instrumented indentation test has emerged as a reliable, easy, quick, and yet non-destructive alternate means to the tensile test to measure tensile-like properties of selective-electron-beam-melted specimens. Furthermore, the macro-instrumented indentation test can be used effectively in additive manufacturing for a rapid setting up of the process, that is, by controlling the microscopic scale properties of the samples, or to quantitatively determine a product quality index of the final builds, by taking advantage of its intrinsic relationship with the tensile properties.

Water-soluble copper(i) complexes bearing 2,2′-bicinchoninic acid dipotassium salt with red-light absorption and repeatable colour change upon freezing operation

The repeatable colour change upon freezing–melting operation of a water solution of a Cu(i) complex is found. Efficient red light absorption is also one of the advantages of this complex.

Logical-mathematical Evaluation Model of Blast-furnace Melting Operation

.

Experimental Study of the Silicon Start-up Heating and Melting Process in an Inductive Cold Crucible

The electromagnetic continuous pulling is a newly growth technology as a promising process for silicon preparation, start-up heating is necessary for the semiconductivity of silicon at room temperature. Investigations were carried out to study this process in a square crucible with the frequency of 50kHz, details of the experimental procedure were given, the affecting factors, electrical performance and heat explosion problems during the process were measured and discussed. The results indicated that the best conditions for the preheating were the central position of the base in the coil, the higher power and the proper primary mass of silicon setting. The electrical performance indirectly showed the pool conditions and so it can be effectively used to control the melting operation.

Melting Automation Using a Medium-Frequency Induction Furnace

Automating the melting process is critical to the economical production of metal castings with stable quality. We discuss manufacturing process monitoring, safety devices, automatic melting operation, and labor-saving furnace refractory construction and dismantling.