http://196.220.128.81:8080/xmlui/handle/123456789/200 2026-08-12T13:31:59Z 2026-08-12T13:31:59Z OLORUNTOBA, DANIEL TOYIN http://196.220.128.81:8080/xmlui/handle/123456789/6022 2026-08-10T15:33:36Z 2002-12-01T00:00:00Z

EFFECTS OF FLUCTUATING HEAT TREATMENT OPERATIONS ON CORROSION RESISTANCE OF AUSTENITIC STAINLESS STEEL SAMPLE IN SULPHURIC ACID SOLUTION OLORUNTOBA, DANIEL TOYIN Corrosion performances of austenitic stainless steel subjected to various cyclic heat treatment operations of normalisation, annealing and solution-quenching have been evaluated. Samples of the as-received material (hot-rolled austenitic stainless steel) were subjected to five cycles of heat-treatment consisting of normalisation soaked for 1 hour and without soaking at 1000°c,annealing soaked for 1 hour and without soaking at 1000ne and solution-quenching soaked for I hour and without soaking at 1000°e. Estimation of corrosion rates from weight loss measurements was carried out using chemical weighing balance of model Mettler AE 160. The results show that corrosion rates decrease with increase in exposure time for as received and heat-treated samples. A general increase in electrode potentials is observed for all the specimens from-235mV (SCE) to-58 mV (SCE) at the exposure periods above 240 hours. The electrode potentials for all the samples remain within the range of-58mY (SCE) and 8mY (SCE) at the exposure periods between 250 and 750 hours. It is concluded that corrosion resistance of austenitic stainless steel subjected to normalization! annealing and solution-quenching at elevated temperature without soaking period at 1000°c is superior to that which was soaked for 1 hour at the temperature. This was attributed to the fact that austenitic stainless steel microstructure remain as austenitic single phase after cooling to room temperature. xviii, 96p. : ill. ; 30cm

2002-12-01T00:00:00Z ADEBIYI, DAMILOLA ISAAC http://196.220.128.81:8080/xmlui/handle/123456789/6020 2026-08-10T15:09:42Z 2006-08-01T00:00:00Z

EFFECT OF CARBON CONTENT ON GRAIN REFINEMENT THROUGH THERMAL CYCLING IN PLAIN CARBON STEEL ADEBIYI, DAMILOLA ISAAC The work investigated the grain refinement achievable In carbon steels by re austenitization and alternate thermal cycling treatments and the properties developed in these carbon steels after cycling at different austenitizing temperatures. Re-austenitization thermal cycling consists of repeated heating to the austenite range; soaking for a short time at the peak temperature and then quenching in water, while the process of alternate thermal cycling consists of alternate heating between the austenite range and the two phase (a+y) range with intermediate quenching in water. The mechanical and microstructural properties of carbon steel with six different carbon levels (0.1%C, 0.22%C, 0.39%C, 0.54%C, 0.81%C, and 1.04% C) were studied at different austenitizing temperatures of 880°C, 900 "c and 920°C. The soaking times were 5, 10 and 15 minutes for 2, 4 and 6 number of thermal cycles. The effect of carbon content on grain refinement of the carbon steels was investigated. It was observed that an optimum temperature exists for grain refinement by thermal cycling treatments and this temperature decreases with increasing number of thermal cycles. For all the holding times investigated, grain size increased with increasing soaking time at the peak temperature, while higher number of cycles requires less holding time. However, with favorable condition of soaking time and peak temperature, grain size decreased with increasing number of thermal cycle up to a certain number after which further cycling does not provide any observable grain refinement but grain coarsening. Repeated austenitization, though accompanied by poor ductility gave higher strength than alternate thermal cycling but the latter produced slightly better grain refinement and better combination of strength and ductility. xiv, 102p. : ill. ; 30cm

2006-08-01T00:00:00Z SALATI, LUQMAN KAREEM http://196.220.128.81:8080/xmlui/handle/123456789/6019 2026-08-10T14:58:54Z 2010-07-01T00:00:00Z

ECONOMIC ASSESSMENT OF MINING TECHNIQUES OF BARYTES DEPOSITS AT AZARA, NASARAWA STATE SALATI, LUQMAN KAREEM This research work presents the economic assessment of mining techniques practiced on veins 1 and 17 of Azara barytes deposits in Nasarawa State. The mechanized, semi mechanized and artisanal mining techniques were appraised based on certain economic indices such as productivity, extraction cost, selling price, importation trend and net profit. Global Positioning System (GPS) was used to take readings of veins 1 and 17 and determine their coordinates which were then transferred to the topographical map. Statistical Package for Social Sciences (SPSS) was used for the statistical analysis of the data collected' for economic indices such as daily, monthly and annual productions and cost of production used for assessing the three mining techniques. The data were subjected to analysis of variance (ANOVA), while Duncan's Multiple Range Test was used to verify significant differences among the treatment means at the 5% probability level. 'Polynomial regression curves between productivity (y) and extraction cost (x) for the different mining techniques were determined using Microsoft Excel (R). Results of the study showed that semi-mechanized method satisfied all the set economic indices more than other methods, thereby emerging as the most suitable mining technique used in the area. Semi-mechanized method recorded the highest productivity of about 33,500 tonnes per annum, while mechanized and artisanal productions were only limited to about 23,908 and 18,050 tonnes per annum respectively, due to technical and financial problems. Results also indicated that lower extraction cost and higher net profit for semi mechanization gave it an edge over other methods, despite its lower selling price and ever-increasing importation level. It was however, observed that lack of funding, poor management, incessant flooding and inadequate working equipment were the greatest obstacles facing sustainable barytes production. Therefore, adequate funding and technical supports have been indicated as a recipe for the re-organization and integration of the present artisanal mining in the area into formal mining sector. xv,104p. : ill. ; 30cm

2010-07-01T00:00:00Z OLASUPO, OLAYODE ADESOLA http://196.220.128.81:8080/xmlui/handle/123456789/6015 2026-08-10T11:51:46Z 2003-09-01T00:00:00Z

DEVELOPMENT OF RAMMING MASS FROM INDIGENOUS REFRACTORY MATERIALS FOR LINING MELTING FURNACES OLASUPO, OLAYODE ADESOLA Aluminosilicate developed refractory ramming masses for lining melting furnaces were from suitable indigenous raw materials. Chemical analyses of the raw materials were done using the Atomic Absorption Spectrophotometer (AAS). Rammed samples from several ratios of clay, silica. mica, bentonite and Durax were prepared using the American Foundrymen Society (AFS) standard rammer and thereafter tested for such properties as apparent porosity. volumetric firing shrinkage, cold compression strength. green compression strength. loss on ignition. thermal shock resistance and refractoriness. The effect of sintering temperature on the physical and the mechanical properties of the samples were studied and reported. Microstructural analyses of some samples were undertaken. Results indicated that 8 ramming cycles was just enough for production of the ramming masses. Two optimal ratios obtained from experiments have a refractoriness of 15000C, excellent thermal shock resistance and good cold compression strength over the sintering temperatures. They therefore qualify to serve as service lining in rotary and crucible furnaces for melting of cast iron and non-ferrous alloys and could serve as a viable alternative to imported ramming masses of the same service temperature. xiii, 77p. : ill. ; 30cm

2003-09-01T00:00:00Z