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Investigation on Mold Flux Melting and Consumption During Continuous Casting of Liquid Steel
No full textMold powders play an integral role in maintaining the stability and efficiency of the continuous casting process as they (1) provide lubrication, (2) control heat transfer, (3) absorb nonmetallic inclusions, and (4) prevent reoxidation of liquid steel during continuous casting of liquid steels. Much of the previous investigations are focused on the characterization of mold powders to understand the physicochemical aspects of the continuous casting process. However, limited attention has been given to analyzing the melting behavior of mold powder, which is necessitated for the proper functioning of the caster. An experimental technique akin to the industrial practice has been adopted in this investigation to study the melting behavior of the mold powder. A realistic nondimensional correlation is proposed considering the various casting parameters (casting speed, mold oscillation frequency, and stroke, negative strip time, and cross-sectional area of mold), the mold powder melting, and the consumption rate based on the adopted experimental and theoretical methods for real-time application
Evaluation of friction welded dissimilar pipe joints between AISI 4140 and ASTM A 106 Grade B steels used in deep exploration drilling
No full textIn the present research work, a detailed evaluation of dissimilar friction welded joints between the hot rolled ASTM A106 Grade B (carbon steel) pipes and hot rolled AISI 4140 (low alloy steel) pipes in the as-received (AR) condition and quenched and tempered (QT) condition has been carried out. All the specimens were subjected to stress relief annealing after welding. Optical and scanning electron microscopy on the AISI 4140 steel side revealed dynamically recrystallized grains, consisting of a mixture of ferrite and martensite in the friction welded AR-condition joints and mixture of ferrite and tempered martensite in the friction welded QT-condition joints. On the ASTM A 106 Grade B steel side the material showed ferrite and pearlite microstructure. SEM analysis did not reveal any intermixing between AISI 4140 and ASTM A106 Grade B steels at the weld interface in both the conditions. The region adjacent to the weld interface on AISI 4140 steel side consistently showed higher hardness in the QT-condition compared to AR-condition due to the presence of fine-grained microstructure in QT-condition. The dissimilar welded pipe joints in the present study have shown slightly higher tensile properties than that of ASTM A106 Grade B steel but significantly lower than that of AISI 4140 steel. The friction welded dissimilar pipe joint specimens have shown substantially lower impact toughness values compared to either ASTM A 106 Grade B steel or AISI 4140 steel in both AR and QT-conditions due to the presence of carbides at the weld interface
High temperature deformation behavior of Indian PHWR Calandria material SS 304L
No full textCalandria, a horizontal stepped cylindrical vessel, houses the fuel channels (reactor core) of Indian Pressurized Heavy Water Reactors (IPHWRs). The Calandria and its support assembly is made from austenitic stainless steel SS 304L grade. Post Fukushima nuclear accident (2011), the realistic assessment of time line of structural degradation of Calandria during the progression of a postulated severe accident has become an important requirement. This calls for a detailed finite element analysis of Calandria assembly where material deformation behavior owing to both creep and plasticity up to very high temperatures arising during accident progression has to be modeled.Although stainless steel SS 304L finds wide application in nuclear industry, the material properties up to very high temperatures as required for present case, are not available in the open literature. Hence, in the present work, the tensile and creep-stress rupture properties of SS 304L have been generated for temperatures up to 1100 °C. Engineering stress-strain curves, yield strength, ultimate tensile strength, uniform elongation as well as Ramberg-Osgood fitting parameters are evaluated from the tensile test data. Creep test data is processed to evaluate creep curves, minimum creep rate, Norton-Bailey creep law parameters as well as Larson Miller Parameter based correlation for prediction of stress rupture life. The generated properties would be useful as material inputs to carry out realistic structural integrity assessment of Calandria assembly for loads arising under accident conditions
Turpentine oil: a novel and natural bridging liquid for agglomeration of coal fines of high ash coals
No full textOil agglomeration is an effective way to demineralize high ash coals as compared to froth flotation and density gradient separation. In this process, the choice of bridging liquid is critical with respect to economics
and efficiency. Herein, we report turpentine oil as a potential bridging liquid which is demonstrably efficient in coal demineralization at lower concentration (10 vol.%) compared to literature (20–25 vol.%) without inclusion of surfactants, which enhances economic viability. We chose two high ash coals of Indian origin, with 26% and
34% ash. A varied range of particle sizes were examined along with pH,type of electrolytes, agitation conditions and oil dosages. Both coals (200 mesh) demonstrated approximately 50% reduction in ash content at pH 7, which is an improvement over previously known reports on Indian coals. Chemical structural resemblance between primary components of turpentine oil and predominant π-delocalized aromatic structure of high rank coals could be the reason behind improved adsorption of oil. Our work thus demonstrated the utilization of a natural oil which can be dried easily, readily available and cheap in a significantly demanding commercial process like coal beneficiation. This is expected to deliver a substantial performance and cost improvement over incumbent known bridging liquids
Journal of Metallurgy and Materials Science : Special Issue on Specialized and Smart Coatings
Get PDFThis special issue discusses different important coatings as well as review on important topic such as corrosion-resistant, self healing, hydrophobic, coatings for turbines, advanced steel coatings, different engineering coatings by PVD process, techniques of understanding interfaces in water splitting and other processes, vacuum furnace designing for industrials applications. I am sure these will enrich the knowledge and help the researchers for deciding many applications and their plans for the developments of advanced coatings
CSIR-NML NEWSLETTER AUGUST- 2021
Get PDFSummary of significant activities
For the period August, 2021,
CSIR-National Metallurgical Laborator
Prospective of titania based photocatalyst for environmental reduction reactions
No full textIn the last two decade photocatalysis is widely studied so as to evolve a green chemical rout to deal with the environmental and energy problem faced by the mankind. Among all the studied photocatalysts anatase TiO2
is most attractive even today though limited to UV light absorption in pure form. However, easy availability, high
aqueous stability and nontoxic nature attracted the researchers to go for different possible modifications. Effort has been made by number of researcher to modify titania through metal, nonmetal doping and mixing with other oxides and sulphides to engineer the band gap, band potential and delay the charge separation through Z-scheme and hetero-junction formation so as to achieve the goal of producing stable and highly active photocatalyst for energy and environmental application. In recent past, various strategies have been tried to extend the solar light absorption from visible to NIR range by using appropriate material so as to ultimately promote the solar photocatalytic performance of TiO2 based composites. Keeping these in view, present review will discuss the past and present development in the area of material modification to deal with band gap engineering, heterojunction formation, required porosity, powder catalyst separation and better charge separation with special objective of improved environmental reduction reactions. In addition future prospect of these materials has been discussed in details for new generation researchers. In particular material based on MOFs, two dimensional materials and metal halide perovskites based titania composites are emphasized for future evaluation to address both air and water pollution
Pulse Electrodeposited Au–WO3 Catalyst from a Water–Ionic Liquid Microemulsion for Photoaccelerated Methanol Electrooxidation
No full textFor improving the separation efficiency of photogenerated carriers and electrocatalytic activity, we have used visible light-responsive tungsten oxide (WO3) as a support for a plasmonic gold nanoparticle (Au NP) cocatalyst. It has been fabricated by a two-step optimized pulse electrodeposition method in aqueous and water-in-ionic liquid microemulsion media. By taking advantage of interfacial heterojunctions and the synergistic effect, the plasmonic Au NP electrocatalyst on WO3-coated fluorine-doped tin oxide as a photoanode has shown enhanced electrocatalytic current density as well as a negative shift in the onset potential under light irradiation for methanol electrooxidation. The pulse electrodeposited Au–WO3 nanocatalyst under light irradiation displays ∼3.85 times enhancement in electrocatalytic activity than without light irradiation, and it has been attributed to the simultaneous enhancement in electron–hole (e–/h+) pair separation of WO3 and Au NP surface plasmon resonance absorption. The mechanism of enhanced electrocatalytic performance of Au–WO3 has also been proposed under light illumination
Mineralogical Study of Beneficiated and Carbonized Indian Coking Coal for Better Utilization: A Case Study
No full textCoking/metallurgical coal is one of the essential raw materials for steel industries. The metallurgical coal in India contains high ash content (mineral matters), is rich in inertinite, and requires optimization before its proper utilization. Distribution of mineral matter in coking coal plays a significant role in achieving the desired product for blast furnace and coke-making operations. The present paper reports a case study on the distribution and nature of mineral matter in Indian coking coals at varying densities with respect to the coal’s beneficiation behavior. The maceral analysis indicated the maximum liberation of reactives at the relative density (RD) of 1.2–1.3 g/cm3 while maximum inerts concentrated at the highest density (RD > 1.8 g/cm3). The most dominating mineral matter found in the coal is argillaceous minerals containing substantial amounts of quartz followed by carbonate and sulfides existing as cavity fillings or in disseminated form. X-ray diffraction (XRD), X-ray fluorescence (XRF), and electron-probe microanalysis (EPMA) techniques were used to study the mineral distribution and transformation behavior of coke produced from the coking coal during carbonization process. A case study on the reactivity of dispersed mineral matter in coke and the implication of mineral transformation behavior on coke is also discussed in this paper
High performance specialized coatings for applications in corrosive environments
No full textIn this paper a short review of various coatings developed based on facile as well as industrially scalable methods and the challenges encountered in enhancing the durability of the coatings in simulated service conditions are presented. These coatings include (i) development of noble metal (Pt/Pd) nanoparticle coated titanium electrodes for electrochemical processes employed in spent nuclear fuel reprocessing, and (ii) development of superhydrophobic (SHP) coatings on titanium, stainless steels, low-chromium steels and copper alloys to address corrosion and biofouling issues in chloride environments of condenser materials in nuclear power plants. Nanostructured noble metal (Pt, Pd) coatings on Titanium and titania nanotube for electrode applications were developed using a novel seed mediated coating technology involving electrodeposition assisted hydrothermal method. Studies demonstrated that by engineering the particle size of Pt, and nano-tubular self assembled arrays of TiO2 (TiNT), the electrocatalytic activity for methanol oxidation could be enhanced ten times compared to polycrystalline Pt. By employing electrochemical cerium oxidation studies, excellent durability of this Pt nanoparticles coated TiNT electrode surpassing 1000 h in 11.5M nitric acid was also demonstrated. In the second part of the manuscript development of SHP coatings to address corrosion and biofouling issues in chloride medium of condenser materials such as titanium, stainless steels, low chromium steels and copper alloys is detailed. Inspired by the lotus effect two step techniques were adopted for creating a micro-nano roughness pattern, and reducing surface energy by coating with low surface energy material. Micro-nano texturing of different materials was achieved by various methods like polishing, pickling, anodization, sand blasting etc. Attempted different organic fatty acids and silica nanoparticles mixed silane, to enhance durability. Finally durable and stable SHP coatings were demonstrated with high water contact angle and corrosion resistance and reduced microbial attachment indicating superior bio corrosion resitance of the materials studied. Facile techniques were adopted for both coatings in order to support scaling up for real time applications in future