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This study was carried out to estimate the gas permeability of coke packed bed in blast furnace. Pressure drop equation was developed by measuring the void change and pressure drop of bed with respect to coke size distribution. The equation was that of Ergun type pressure drop equation. As the coke-ore size ratio increased, the pressure drop of coke-ore double layer rose due to the decrease in void volume at coko-ore interface. The pressure drop of double layer was found to be higher than that of coke-ore mixture.

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Dynamic fracture toughness of a structural steel has been estimated by employing instrumented impact testing method with small size specimens. One of the pendulum type impact testing machines equipped with semiconductor strain gage block in the tup, was used in this study. Signal from the dynamic transducer was multiplied by a dynamic strain amplifier and then stored in a digital memory before analyzing. Experimental results demonstrated that the toughness obtained from the instrumented impact testing agreed well with theoretical value, but several factors were appeared to play an important role when converting the test results into dynamic fracture toughness based on linear elastic theory. They were (1) the crack initiation point which would occur prior to maximum impact load, Pm, on the load-deflection curve, (2) compliance correction and (3) elastic inertial wave effect which had nothing to do with the specimen toughness.

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In order to find out the formation procedures and the series of morphology for silicon nitride by the vapor phase reaction, the experiments have been carried out in the temperature range of 200-1550℃ and the various pressures. The reaction products and thermal decomposited powders in the various temperatures and pressures kave been thoroughly investigated by means of X-ray diffraction, infra-red spectroscopy and electron microscopy. As regards to silicon nitride powders, crystallized whisker shaped α-Si₃N₄ was obtained by treating the reaction product formed at 25℃ into 1450℃. At 1550℃ under the pressure of 2.9KPa, hexagonal shaped α-Si₃N₄ was obtained in the thermal decomposition, and rod shaped β-Si₃N₄ in the vapor phase reaction.

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In order to find out the formation procedures and the serves of morphology for aluminum nitride by the vapor phase reaction, the experiments have been carried out in the temperature range of 200-1500℃ and the various pressures. The reaction products and thermal decomposited powders in the various temperatures and pressures have been thoroughly investigated by means of X-ray diffraction, and electron microscopy. Sphere shaped A1N was formed from 600℃, whereas whisker-shaped and rod-shaped A1N crystals were obtained in more than 1000℃ in the vapor phase reaction. For aluminum nitride powders, the growth of crystal was accelerated at constant pressure of 4.9 KPa. A1N formed by these reaction is changed gradually into sphere, plumule, and rod-shaped with increasing temperature.

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The methods of Cr-addition on a low-C steel affect the properties and the formation of a Cr-surface-alloyed layer produced by CO₂laser. The depth of melted zone showed larger in a Cr-electroplated specimen than in a Cr-powder coated one, while the width of melted zone on surface showed reversed results. The hardness of surface alloyed zone in a Cr-electroplated specimen resulted lower than that of matrix as other investigators had reported. Meanwhile that in a Cr-powder coated specimen increased very high due to some precipitations and the phase transformation. There is a tendency in the Cr-powder coated specimen for Cr to be penetrated and dispersed in melted region deeply compared with in Cr-electroplated specimen. In order to enhance the wear resistance on the Cr-surface-alloyed zone by laser, it is desirable to use the method of Cr-powder coating on low-C steel.

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The static and cyclic creep behaviors of base and longituinally welded AISI-304L stainless steel have been studied. The weld specimens were welded by SMAW (Shielded Metal Arc Welding) process, and crept under control load condition at 803-873 K using electro servo-hydraulic testing machine. The results of static and cyclic creep tests showed that longitudinally welded metal behaves like composite material. Using static and cyclic creep test results and tensile test data, the creep behaviors of welded metal were quantitatively analysed and compared with experimental results. In the case of static creep, the following equation was obtained between the creep rates of base and welded metal. (수식) In the case of cyclic creep, negative creep stages were observed at the initial cycling period. This negative creep strain were believed to be due to the cyclic hardening of base metal and the following relationship was satisfied. ΔεαΔσ_(base) Δσ_(base) : Cyclic hardening of base metal.

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Cold-rolled sheet steel for automobiles requires high strength and good drawability, for that purpose P-bearing low carbon, low maganese Al-killed steel is investigated. For various coiling temperatures on hot rolling stage, the effects of coiling temperatures on textures and deer-drawability of P-bearning steel were investigated by 1) pole intensity analysis 2) Transmission Electron Microscopy 3) plastic strain ratio determination from tensile test. No apparent changes in textures of hot-rolled sheet and cold-rolled sheet were detected within the range of coiling temperatures examined. The optimum coiling temperature for good recrystalization texture, high average strain ratio (R) and low planar anisotropy (ΔR) after recrystallization annealing was 600℃. However, differences in their characteristics were very slight except the specimen of coiling temperature 700℃ However, since the maximum tensile strength of the specimen was obtained when coiled at 600℃, optimum coiling temperature which could provide good deep-drawability while sustaining high strength might be concluded to be around 600℃ in this steel.

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