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Dynamic fracture toughness of a hull structural steel has been investigated. Thermal cycles simulation and instrumented impart testing technique were employed to obtain the dynamic fracture toughness of welds utilizing small size specimens. Microstructural change of nomnmetallic inclusions during cooling process was also discussed. Experimental results showed that the dynamic fracture toughness of simulated welds, which displayed relatively lower toughness values compared with that of the base metal, was decreased as the critical cooling time was increased. Sulfide-type nonmetallic inclusions in the welds microstructure were observed, and their elongated morphology had been changed into spherical shape during the welds thermal cycling.

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Understanding of the pattern of molten steel through a mold in the continuous casting is a precondition for estimating and avoiding negative effects on steel cleanness. To study the flow pattern in the mold, experiments were carried out using a ½ scale water model of the mold. The stimulus - response method and the pictures of the flow pattern taken with an elaspe - time technique were used in order to study the flow pattern developed. The velocity field was predicted by solving the turbulent clavier - Stoke`s equations using the K-ε model for turbulent viscosity. There were a good agreements between the water model results and the computed results. The studies also gave some information on removal of nonmetallic inclusios.

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An evaluation of Hydrogen Induced Cracking (HIC) susceptibility of low alloyed high tensile strength steels with different microstructure were conducted both in a synthetic seawater saturated with H₂S (BP solution) and in an acidified chloride solution saturated with H₂S (NACE solution) at room temperature according to standard test method (NACE TM-02-84). Threshold diffusible hydrogen content (C_(th)) value of each steel was also determined, which was shown to be a consistent indicator in the determination of HIC susceptibility Standard HIC test showed comparatively low reliability due to a wide allowable range of H₂S concentration for the `saturated condition`(2300-3500ppm), which could be compensated by incorporating C_(th) value. Moreover, the C_(th) values determined from cathodic charging of hydrogen agreed well with those determined from the standard test; the method, therefore, is proposed as an easy, reliable method for measuring HIC susceptibility of steels for sour service.

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The effects of nitrogen and delta ferrite contents on 700℃ creep behavior of AISI 304 duplex weld metal under constant stress conditions were investigated. High ferrite weld metal showed a ductility almost as high as that of base metal under high stress. However, the ductility decreased sharply due to the sigma phase transformation under law stress. Distinct dislocation substructure was formed in high ferrite weld metal during creep deformation. On the other hand, the nitrogen in low ferrite weld metal formed nitrides during creep, which hindered dislocation motion and increased the creep strength remarkably. Activation energy for creep of weld metal increased with nitrogen content. This observation could be explained by a dynamic strain hardening effect and a decrease in diffusion rate due to nitrogen atoms.

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Adsorption rates of gold thiourea on activated carbon were determined in solutions circulated through the activated carbon bed as a function of initial gold concentration, pH of solution, amount of carbon, flow rate of solution circulation and adsorption temperature. Results thus obtained revealed that the adsorption behavior of complex ion (Au(CS(NH₂)₂)＾(+)₂on activated carbon follows generally the charge collection theory and also applies to Freundlich adsorption isotherm as well as Elovich equation.

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Recrystallization behavior of martensite of Fe-32%Ni alloy has been studied with hardness measurement method. Hardness vs. temperature curves at all deformation degrees consist of two steps: first step is due to reverse transformations from martensite to austenite, and second step recrystallizations of reversed austenites. Recrystallization of martensite necessarily occurs after reverse transformation from martensite to austenite, and the recrystallization temperature is decreased with increasing deformation degree. Activation energy for recrystallization is also decreased with increasing deformation degree. From the discussion of the activation energy, it is suggested that the recrystallization is controlled by nucleation process. Reverse transformation temperature (As) becomes higher as the deformation degree is increased.

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The fracture toughness of ductile cast irons having substantially different microstructures due to Sn addition was studied. The effect of the notch tip diameter on the fracture toughness was also studied. The conditional fracture toughness, K_Q was found to decrease by approximately 50 to 60% with Sn addition. Considering general mechanical properties and fracture toughness, it was concluded that tin addition for strengthening ductile cast iron should be restricted within 0.1%.

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A review on the parameters controlling the solidification rate of droplets, the rapid solidification techniques of metal powders, the various effects of rapid solidification, the dendritic and microcrystalline structures which are the basic microstructures in rapidly solidified metal powders, and the estimation of heat transfer coefficient and solidification time is presented.

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