A Study of the Microstructure,Mechanical Properties and Weldability of Low-carbon Ductile Iron

Abstract

Low-carbon cast iron (1.7–1.8% C, 1.7–2.2% Si) test bars and castings were prepared in a production foundry for evaluation of their microstructures and mechanical properties. The experimental variables were (a) inoculant types and (b) heat treatment cycles. Results indicate that low-carbon ductile cast irons with graphite present in spheroidal/compacted form may be satisfactorily produced on an industrial scale, after appropriate inoculation. However, a short normalising cum tempering heat treatment is necessary for the development of optimum mechanical properties. Low carbon irons can be satisfactorily welded to similar grades of cast irons as well as to steel.     

Processing of duplex stainless steel by WEDM

This study investigates the manufacturing process of 2205 duplex stainless steel by wire electrical discharge machining where the effects of pulse-on time (PONT), wire tension and pulse-off time (POFT) on surface finish, kerf width, and material removal rate (MRR). It was found that the kerf width was unchanged with the change of PONT at long pulse-of time and higher wire tension. However, it decreased initially and then increased due to the rise of PONT at low values of wire tension and POFT. Low wire tension and PONT, POFT and contributed towards widest kerf. Longer PONT increased MRR due to higher machining/processing speed. Lower wire tension and shorter POFT increased MRR more than that of higher wire tension and POFT. Craters and recast layer were on the machined surfaces at all machining conditions. Increased PONT raised surface roughness at the lower POFT and tension in the wire. The surface finish at high wire tension and longer PONT is always better than that at smaller PONT and lower tension in the wire. The microstructure underneath the recast layer remains unchanged and the failure of wire electrode occurred at higher wire tension, longer PONT and shorter POFT.     

The formation and perception of safety,danger and insecurity inside gated communities: two cases from Istanbul,Turkey

This paper will explore safety and danger in gated communities in Turkey, an important subject of study in recent research in urban studies, conducted nationally and internationally. Safety has become a major concern in the last years, especially in large metropolises, leading people to move to gated communities which are thought to protect residents from urban problems. The paper uses the data collected during a fieldwork conducted in two gated communities in Istanbul. The main data is based on semi-structured in-depth interviews with their residents and other participants providing first-hand information on two case studies. The paper also uses visual and statistical data provided by relevant administrative officers. The paper indicates that gated communities are not totally isolated and ready-made sites. Rather, it argues that they create a mixture of “traditional” and “ready-made” safety while they also lead to new forms of danger, all of which emerging from their different socio-spatial configurations.     

Manipulation of slag separation properties from pig iron nuggets with flux additions to dried greenball mixture

Pig iron nugget process is one of the direct smelting processes developed as an alternative to the traditional blast furnace process. Throughout the process, slag-free pig iron nuggets, which have similar properties to the blast furnace pig iron and white cast iron, are produced by single-stage heat treatment of dried greenballs. During the process, slag separation from the metallized areas can be enhanced by adjustment of the slag’s chemical and physical properties. The objective of this research was to investigate the effects of flux addition rates (basic to acid ratio) to the dried greenball mixture on pig iron nugget production and slag separation. Thus, this study involved the heat treatment of six different greenball mixtures, which contained various amounts of limestone addition (basic to acid ratios, 0, 0.63, 1.02, 1.42, 1.85, and 2.29) utilizing a laboratory-scale resistance box furnace or simultaneous differential scanning calorimetry and thermalgravimetric analyzer. The samples produced by heating in the box furnace were analyzed for their morphological and chemical properties utilizing optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), macroscopic observations, iron titrations, and atomic absorption spectroscopy. It was determined that the highest percentage of iron yield in the nugget for the process and the highest distribution of iron in magnetic slag were obtained when utilizing the greenball mixture, which contained 7.5 wt% limestone as flux (basic to acid ratio of 1.42).     

Chain extension of recycled PA6

Recycling of polymers is a necessity in our intensively consuming polymer world but the nature of polymers is such that they are prone to thermal degradation when re‐extruded and this poses technical challenges to recycling. This article describes research that seeks to rebuild the structure of degraded PA6. We present data from controlled experiments with pristine pPA6 extruded to form a base recycle rPA6 to which we added two chain extenders, separately: one with anhydride multifunctionality (ANHY), highly reactive with amide groups and one with epoxy multifunctionality (EPOX), less reactive. We found from rheological data carried out in the linear viscoelastic region (so as to study structural changes) a striking difference in the ability of the chain extenders to rebuild structure: 306% increase in the complex viscosity of rPA6/ANHY compared to 25% in that of rPA6/EPOX of the base rPA6. Mechanical and thermal (DSC and TGA) tests confirmed the superior efficacy of the multifunctional anhydride chain extender. Beside the practical benefit that ensues from this research, it also provides a strategic platform to develop chain extenders for other degrading polymers on the basis of understanding the degradation chemical reaction and targeting the most reactive end group of the split chains. POLYM. ENG. SCI., 58:1037–1042, 2018. © 2017 Society of Plastics Engineers     

Interlaboratory proficiency testing: Intercomparison in relation to the measurement of alumina,iron(III) oxide and Titania present in homogenised china clay

For establishing technical competence in testing and calibration, a laboratory has to participate in proficiency testing (PT) program from time to time. An intercomparison in the field of chemical analysis using classical and instrumental methods of analysis has been carried out by 17 accredited as well as non accredited laboratories in India as per requirement of National Accreditation Board for Testing and Calibration Laboratories(NABL), New Delhi. Central Glass and Ceramic Research Institute(CGCRI), Kolkata acted as a nodal laboratory and conducted this PT programme during 2000–2001. This paper reports the analytical results and statistical evaluation of the results using Z-score.     

A new microwave processing strategy for food-ceramic composite layer confined within ceramic plates

A theoretical analysis has been carried out to study the efficient microwave processing of discrete food sample ceramic composite attached with ceramic (Al₂O₃ and SiC) plates. Continuous food sample with a specific thickness corresponding to smaller power absorption is replaced by two discrete samples and processed with ceramic composite. The effective power and temperature distribution are found to be function of discrete food sample ratios, type of microwave incidence and ceramic layer thickness. The effect of ceramic material on various discrete sample ratios have been studied via effective average power vs. thickness of ceramic (Al₂O₃ or SiC) intermediate for one side and both sides microwave incidence. It is found that power absorption is enhanced significantly for beef sample due to specific thickness of ceramic composite corresponding to one side microwave incidence. The power enhancement is lesser and the temperature difference or thermal runaway is larger for bread samples as compared to beef samples. The enhancement of heat absorption is larger for one side incidence as compared to both sides incidence with identical total intensity of microwave incidence. The role of discrete samples with ceramic composites is significant for highly lossy substances (beef) whereas the composites do not play significant role on optimal processing of low lossy substances (bread).     

Sol-Gel Synthesis of Zn Doped MgO Nanoparticles and Their Applications

Abstract

The physicochemical properties of metal oxide nanoparticles can be significantly improved by doping. MgO and Zn²⁺ doped MgO (Zn:MgO) offers potential applications in photonic devices falling in the UV and visible region. In the present paper, sol gel method was employed to synthesize pure and Zn²⁺ doped MgO nanoparticles. XRD pattern inferred the crystalline nature of material and also the slight change in peak due to the dopant. FESEM showed the formation of nanoparticles with almost same shapes and dimensions with little agglomeration. Optical properties were studied by using UV-Vis and PL techniques. Doping of Zn²⁺ in MgO nanoparticles was verified by EDS.     

Optimizing dimensional accuracy of titanium alloy features produced by wire electrical discharge machining

This study investigates geometrical errors such as cylindricity, circularity and diametral errors of a feature (a hole) produced from wire electrical discharge machining of Ti6Al4V alloy where tension in wire, pulse on time, and flushing pressure are varied. Pareto analysis of variance (ANOVA), Taguchi design of experiment (DoE), and traditional analysis estimate the influence of variables on errors of holes. It was noted that flushing pressure is the most significant factor with individual contributions of 31.02%, 49.5% and 37.84% to circularity, cylindricity, and diametral errors, respectively. The circularity error of holes decreases as the flushing pressure and tension in wire rise, but decreases with the rise of pulse on time. The cylindricity error decreased with the increase of wire tension, flushing pressure and pulse on time. The absolute diametral error reduced as the pulse on time and tension in wire raised, but it raised with the rise of pulse on time. All these trends are associated with the influence of tension in wire on the flexibility of wire, the dependence of heat generation and dissipation on pulse on time, and ability of the flushing pressure to control the cooling, as well as debris removal from the machining zone.