Materials Science Forum Vol. 978

Abstract: Weld and surface properties of Al 1100 alloy by incorporating graphene nanoparticles, different varieties of graphite and CNTs interlayer has been studied here. The incorporation of different carbonaceous interlayers was achieved by drop casting and alloy plates were joined together by resistance spot welding technique. A single optimum welding current and time parameter was chosen by trial and error method. Lap shear tests were carried out to find the peak load bearing strengths of the alloy plates processed at the constant welding current and time conditions and a comparison of the weld strength is made. Highest load bearing capacity was exhibited by the base material as compared to that of carbonaceous nanoparticles. Microstructural characterization was done by optical microscopy and SEM. XRD was carried out to find the formation of any intermetallics or phases during the processing. Fractography was studied to analyze the underlying fracture mechanism. Micro-hardness of the Al samples processed with different carbonaceous reinforcements was found out and the maximum hardness was exhibited by the finer sized carbon nanoparticles. A comparative study is being made between the various carbonaceous nanoparticles employed here.

Abstract: Presence of non-metallic inclusion deteriorates quality of steel and causes nozzle clogging during casting. Nozzle clogging eventually leads to a disruption of normal casting operations. This happens when solid alumina inclusions get accumulate in the nozzle of submerged entry nozzle (SEN). Therefore, it is required to understand the inclusion characteristics (shape, size and chemistry), which forms during the steelmaking process. Calcium is added in the steel ladle furnace (LF) in the form of CaSi wire to modify inclusions and to desulphurize steel. The range in which all the oxides become liquid and no solid sulphides begin to form is regarded as the "optimum window" or “liquid inclusion window” for calcium treatment. It is a target to obtain this calcium addition window, during calcium addition in the ladle furnace. This window mainly depends on the sulfur and total oxygen contents of the liquid steel bath. In the present study, inclusions characteristics such as volume fraction of inclusions, inclusion rating and EDS analysis of inclusions has been carried out using SEM-EDS. Thermodynamic study is carried out using thermodynamic software FACTSAGE and databases to find out formation of various calcium aluminates and the precipitation of CaS. Results show that liquid inclusion window mainly depends mainly on the sulphur level, total oxygen and aluminum content in the steel. These windows will help in calculation of calcium addition range for optimizing the addition of calcium in the ladle. These nomograms have been validated with actual plant condition to reduce the nozzle clogging during continuous casting.

Abstract: Sticking of alumina as well as spinel inclusions inside the sub entry nozzles (SEN) as well as tundish nozzle is perennial problem during continuous casting of aluminum killed steel through billet casters. This results in restriction or completely blockage of flow of liquid steel through the nozzles eventually leading to abortion of sequence in billet casters and stopping of continuous casting machine. Nozzle clogging not only restricts the productivity by restraining the casting sequence, intermittent extrication of clogged alumina particles or dislodged refractory materials are a significant source of non-metallic macro-inclusions in the cast sections of billet casters. If these inclusions are not removed completely during secondary refining of steel they causes excessive clogging mainly in low carbon Al killed steels. In other grades of Al killed steel cogging is also very prominent if the deoxidation and secondary refining is not carried out properly. IISCO Steel Plant (ISP), Burnpur a new, modernised unit of Steel Authority of India Limited (SAIL) was facing problems of nozzle clogging in low carbon, low Si, Al killed grade (EWNR –electrode quality grade) resulting in premature abortion of casting sequence leading to huge productivity loss. To solve the problem of nozzle clogging in low carbon Al killed grades and other grades at ISP, optimisation of various steelmaking parameters viz. amount of Al addition & its sequence, purging regime in ladle furnace, optimisation of Ca treatment process etc has been carried out which has resulted in improvement in castability of Al Killed Steel in billet caster of ISP.

Abstract: Green sand mixtures which are used for moulding purposes in foundry industries should possess sufficient green compression strength, flowability, toughness and air-permeability. Usually, the aforementioned properties for a particular casting differ due to variation in composition of the moulding sand mixtures, sand grain shape and size, bonding capacity of the binder, type and quantity of additives used, etc. The present work focuses on the effect of various additives namely, camphor powder, coconut shell ash, mixture of camphor powder and coconut shell ash at diverse proportions on permeability and green compression strength of the sand moulds. The quantity of the aforementioned additives for experimentation was varied from 0.5 to 3.5 wt. %. It was found that the mould’s permeability increased on addition of 1 wt. % additives for all cases. Similarly, the optimum quantity of additives that needs to be added to the sand mixtures for enhancing green compression strength was found to be 2 wt. %. Among all the additives used for improving the mould’s permeability, substitution of camphor exhibited best results. The green compression strength was found to be highest for the coconut shell ash containing sand mould. The moulding sand containing a combination of camphor powder and coconut shell ash between 1 to 2 wt. % exhibited fine mould permeability along with sufficient green strength.

Abstract: To effectively interpret the fluid flow dynamics in the molten metal pool, a numerical model was established. The moving repetitive Gaussian laser pulse is irradiated in the work piece. The consideration of laser scanning speed makes the transport phenomena complex. The continuity and momentum equations are solved to get the flow velocity of the molten metal in the melt pool. The energy equation is solved to know the temperature field in the work piece. The algebraic equations obtained after discretization of the governing equations by Finite Volume Method (FVM) are then solved by the Tri Diagonal Matrix Method. Enthalpy-porosity technique is used to capture the position of the melt front which determines the shape of the melt pool. Marangoni convection is considered to know its effect on the shape of the melt pool. The surface tension coefficient is taken as both positive and negative value while calculating the Marangoni force. The two possible cases will cause the Marangoni force to distort the flow dynamics in the melt pool . It's dominance over the buoyancy force in controlling the melt pool shape is focused in the present study. Further, the present model will present an insight to the consequences of laser scanning velocity over the melt pool dimensions and shape.

Abstract: The present paper describes the Lead dispersion in hypoeutectic Aluminium-Silicon alloys and their microstructural characteristics. The homogeneous dispersion of Lead (Pb) in Aluminium-Silicon alloys (Al-6Si+Pb (=0, 10, 15, 20, 25)) were fabricated by using of spray forming technique (also known as spray casting or spray deposition) in the form of near-net shape disc. The microstructural characterization has been done for different location of spray formed disc by using optical microscopy (OM), Scanning electron microscopy (SEM) and X-Ray Diffraction (XRD) respectively. The results of the optical image were exhibited the equiaxed and globular grain morphology of primary Aluminium with the homogeneous dispersion of extremely fine and malleable particles of Lead and spherical particles of silicon in α–Aluminium matrix. The dispersed Lead has seen clearly in the SEM images of spray formed Aluminium-Silicon alloys and result of XRD pattern confirmed the phases of Aluminium-Silicon and Lead. The grain size of Aluminium has been analyzed by intercept line method. The lattice parameter and lattice strain have been calculated with the help of the XRD pattern to determine the effect of Lead dispersion on Al-Si alloy.

Abstract: Electric Discharge Machining (EDM) is a thermo-electrical disintegration process, utilized to cut hard materials into complex shapes. In EDM, the three vital components are work-piece material, electrode material and dielectric liquid. The significant function of the dielectric fluid is to produce a breakdown voltage for creating a spark between work-piece and electrode. This spark creates ionization by plasma generation and it expels the material from work-piece. In most cases, hydrocarbon-based dielectric liquid is preferred in the EDM process. This kind of dielectric liquid generates hazardous gases which are harmful to people, environment and ecological balances. In this experiment, Canola oil is utilized and the outcomes are compared. The input parameters are Pulse on/off time, current and gap voltage. Copper, Brass and Tungsten-Copper (Alloy) are used as electrodes. The output values from the experiments are Surface Roughness (SR), Electrode Wear Rate (EWR) and Material Removal Rate (MRR). The outcomes demonstrated that Canola oil-based dielectric fluid has comparable properties of conventional based dielectric fluid. This Canola based dielectric gives more prominent MRR value than EDM oil-based dielectric liquid and furthermore higher EWR and SR values are recorded. The proposed Canola oil-based dielectric fluid is biodegradable and has improved suitability in machining.

Abstract: The quality and geometry of deposited bead depend on their input process parameters and their interaction effects in fusion welding process. Minimum dilution and maximum bead size are the most desirable property in material processing applications. The effects of process parameters on dilution and bead geometry have been analysed during material deposition by Plasma Transferred Arc Welding (PTAW) process using the response surface method. The experimental data are used for modelling using three level factorial techniques. The mathematical models have been developed for bead height, width and dilution. The accuracy of the models has been checked using the analysis of variance. The effects of process parameters on bead geometry and dilution have been investigated.

Abstract: Enhanced tool life of cutting inserts are most suitable condition for higher productivity of a manufacturing industry. Several methods are found and employed for higher tool life of cutting inserts among which cryogenic treatment is considered as the most significant method but no adequate researches have been found concerning the impact of cryogenic treatment on cermet inserts especially in hard turning operation. Hence, in the current experimental investigation, the comparative assessment of various responses such as flank wear, crater wear, chip morphology, and chip compression ratio were carried out during machining of hardened steel with both untreated and cryo-treated cermet inserts under dry cutting condition. Wear on the rake faces and flank faces were studied using advanced optical microscope, while chip morphology was studied using SEM. The experimental result demonstrated that the uncoated deep cryotreated with tempered cermet insert delivered better results in comparison to other cermet inserts. Deep cryogenically treated with tempered insert was found to be more suitable during machining of hardened steel because of the enhancement of wear resistance, micro hardness and toughness.