During charging, tapping, hot repairing, and idling, the refractory lining also comes into direct contact with the air. Oxidation of MgO-C refractories containing 20 wt-% At the face opposite the hot face of the refractories, the graphite was conducted by measuring the weight loss temperature is low and the face may also come into contact at regular intervals at various temperatures from 800 with air which comes through cracks, crevices, etc. Besides to 1600°C in air. T he rate of decarburisation increased direct air oxidation, FeO present in slag plays a significant with rise in temperature from 800 to 1400°C and then role in the oxidation of carbon in MgO-C bricks. remained more or less constant from 1400 to 1600°C.Oxidation of carbon and its prevention is a subject of T he oxidation kinetics were analysed in detail and great interest in the field of BOF refractories. Different reaction rate models derived for the temperature range techniques1-6 have been used for studying air oxidation of 800-1400°C. T he reaction rate was found to be con-MgO-C samples. In the present work, it was studied under trolled by diVusion of oxygen through the decarburised isothermal conditions by measuring the weight loss at layer. At higher temperatures (>1400°C), oxidation regular intervals. One of the most important parameters is of graphite also takes place indirectly by the reacobviously the temperature. When heated in air, carbon is tion MgO(s)+C(s) Mg(g)+CO(g). T he magoxidised at temperatures from around 600-700°C to form nesium vapour thus produced is reoxidised at the outer CO or CO 2 . Oxidation studies were, therefore, conducted surface and redeposited as MgO. T his leads to a at various temperatures ranging from 800 to 1600°C. reduction in porosity in the decarburised outer shellAlthough MgO-C bricks can contain from 5 to 35 wt-% and, consequently, a reduction in the rate of oxidation. carbon, the amount of carbon usually ranges from 5 to BCT /364 20 wt-%. It was, therefore, thought appropriate to study the effect of temperature on MgO-C specimens containing At the time the research was carried out the authors 20 wt-% graphite.
A new boundary element formulation for linear elasticity problems is presented in this paper. The standard formulation for planar problems uses two kernels — one of which is logarithmic singular and the other is 1/r singular, where r is the distance between a source and a field point. The new formulation avoids the use of the strongly singular kernel so that both kernels are now only logarithmic singular. The new formulation has several potential advantages over the standard one, the most significant of which is that it delivers stresses accurately at internal points which are extremely close to the boundary of a body. Numerical results for sample problems, from each of the formulations, are presented and compared here.
Let H denote the class of harmonic functions f in D := {z ∈ C : |z| < 1} normalized by f (0) = 0 = f z (0) − 1. For α ≥ 0, we consider the following classIn this paper, we first prove the coefficient conjecture of Clunie and Sheil-Small for functions in the class W 0 H (α). We also prove growth theorem, convolution, convex combination properties for functions in the class W 0 H (α). Finally, we determine the value of r so that the partial sums of functions in the class W 0 H (α) are closeto-convex in |z| < r.1991 Mathematics Subject Classification. Primary 30C45, 30C80.
MgO-C refractories are extensively used in metallurgical vessels in the steel industry. The graphite plays a vital role owing to its non-wettability with slag. Though quality is very important for graphite, little published data is available on the effect of varying ash content on oxidation. Since MgO-C bricks manufactured from graphite with different ash contents are regularly used for lining converters and steel ladles at SAIL plants, a study has been conducted to select an optimum graphite with low cost. Graphites with 2 . 8, 4 . 4, 12 and 20% ash content were used to make MgO-C samples in the laboratory, and oxidation properties were evaluated using an electrically heated tube furnace. Kinetic analysis shows that a chemical reaction mechanism operates in the earlier part of oxidation, followed by a diffusion mechanism in the latter part. MgO-C manufactured from graphite with 4 . 4% ash content was observed to have the best oxidation resistance, with an activation energy of 43 . 4 kJ mol 21 during the earlier stage followed by 34 . 2 kJ mol 21 in the latter.
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