발간논문

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Delamination mode and effect of delamination on the impact toughness and transition temperature were studied in (i) conventionally rolled carbon steels with considerable amount of elongated MnS inclusions, and (ii) controlled rolled HSLA steels with only small amount of S and globular sulphide inclusions. The observed phenomena were explained in terms of delamination mechanism, stress state and distribution, stress pulse duration, and fracture energy.

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The Steel plant is composed of many sub-plants which perform their own processes and among these processes the batch processes related with the ingot process are very important with respect to the process optimization, for they generally determine the extent of the realization of the process optimization. In this research the mathematical model for the prediction of the soaking of the which optimizes the ingot process of the 2nd Blooming and Stabbing Mill Plant of the POSCO is developed. This article deals the development of the simultion model for the 2nd Blooming and Stabbing Mill Plant of the POSCO. The energy saving more than 10% is shown to be realized by applying the above simulation model manually. Therefore the process optimization of the 2nd Blooming and Stabbing Plant of the POSCO is anticipated by the computerization of the above plant which is now undergoing.

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Fluid motion of bath and the depth of cavity have been studied by water model experiments. The results obtained are as follows. 1. Fluid motion of bath depends of flow rate of gas and height of lance. 2. The experiment shows that depth of cavity in bath by top blowing could be expressed as the equation u.d.＝171.3 (L+h)√L which is higher than theoretical value (α＝125.4) because of decreases energy.

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A computer program has been developed for the calculation of inter diffusion coefficients from the experimental data of the infinite diffusion couples having continuous diffusion paths in ternary systems. Introducing the least square method for the smooth curve fitting to experimental data over again, one can minimize the shock of inevitable experimental errors to the results of numerical calculation. Using the second integration method of Boltzmann-Matano`s equation, one obtains that the value of numerical calculation is more accurate than that of graphical calculation at extremely lower or upper concentrations especially.

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A study on the dynamic recovery and recrystallization behavior of 2014 Al alloy has been made using torsion test at the temperature range between room temperature and 510℃. The shear strain rate in the test varied from 0.025 to 0.5/sec. The flow curves showed characteristics of dynamic recovery and recrystallization. The dynamic recovery was favored at the condition of higher temperature and lower strain rate. The strain for the strain softening increased with increasing Zener-Hollomon parameter. The maximum torque Mt(p) and the steady state torque Mt(s) were given, respectively, by Mt(p) (in Kg-m) = 9.074×10^(-3) [γ°exp (9.475×10³/T)]^(0.42) Mt(s) (in Kg-m) = 7.62×10^(-3) [γ°exp (1.329×10⁴/T)]^(0.28)

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