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Deep drawability of a 0.03C-1.6Mn-0.08P-Fe dual-phase steel was improved by pre-treatment of box-annealing. Lankford value became larger with slower heating, higher annealing temperature, and longer annealing time. The pre-treatment produced carbide or pearlite aggregates along grain boundaries, which were readily transformed to austenite by the intercritrical annealing and then to martensite by the followed cooling. This made possible to produce dual phase structure with slower cooling rates. The (111) [112] texture which was developed by the pre-treatment was mostly mantained after the intercritical annealing.

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The crack opening displacement (COD) test has been applied to evaluated the fracture toughness as a function of specimen size for ABS EH 36 steel. The results obtained in the present works can be summuized as follow; 1. Critical COD value decreases initially with increasing specimen thickness and become constant above of SOmm in thickness. 2. The Critical COD was influenced more by the specimen thickness than the specimen Orientation. 3. The Size of specimen for high toughness materials, such as ABS EH 36 steel, should be greater than that of BS 5762.

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A bell-less top has been installed for the second campaign of Pohang No.2 Blast Furnace (working volume 2550㎥) for the first time in POSCO. In consideration of its high flexibility in controlling burden distribution in the furnace, this experiment was performed using a full scale model before blowing-in. Various tests were carried out in order to secure a burden distribution technique and the results have been applied to the actual operation. As a result, good operational conditions have been established,

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A study on the effect of Pb and Cu in zinc ore is executed for a preventive measures of the fluidized bed agglomeration during the roasting of zinc concentrate. The more the contents of Pb and Cu in zinc concentrate increase, the more the amount of agglomeration increases. Especially, when the contents of Cu in zinc concentrate is over 2.5wt%, the roasting process is very hard. The more the roasting temperature increase, the more the amount cf agglomeration increases during the roasting of the concentrate (Pb 1.5%, Cu 0.7%), and the sorts of compound in agglomerating calcine get to be different. Namely, at 850-950℃, the agglomerating calcine contains ZnO, ZnO·Fe₂O₃,CuSO₄, 2PbO·PbSO₄4PbO·PbSO₄and 2PbO·SiO₂, etc.. At 800℃, 4PbO·PbSO₄is not contained, but at 750℃, ZnO, ZnO·Fe₂O₃, CuSO₄and PbSO₄are contained. When air blowing increases, the agglomeration decreases. In the effect for the change of particle size, when the size decreases, wt.% of bed agglomerating calcine decreases. In these experimental results for the preventive measures of the fluidized bed agglomeration, Pb and Cu in zinc concentrate must decrease less than 0.5%, 0.2% respectively, and air blowing must occasionally increase.

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From the study on the thermal decomposition and oxidation of arsenopyrite of Ulsan mine, the following results were obtained. 1. The thermal decomposition of arsenopyrite was found to begin from about 440℃ and its products were metallic arsenic and ferrous sulfide. 2. The optimum temperature of oxidation roasting was in the range of 490-510℃ which was the ignition temperature of the arsenopyrite. 3. In the case of the oxidation roasting of the arsenopyrite at high temperature above 590℃. As couldn`t be sufficiently oxidized to form the desired arsenictrioxide, thus it was contaminated with the metallic arsenic.

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Many studies have been done to explain the effect of grain boundaries in austenite shell on the growth of spheroidal graphite . But, its effect on the melting procedure of spheroidal graphite cast iron is unknown. Therefore, in this work, melting procedure of spheroidal graphite cast iron and the role of grain boundaries in austenite shell on melting of spheroidal graphite have been studied, by changing the condition of melting and the content of phosphor. The main results are summarized as follows. 1. Steadite melts under the eutectic temperature. Therefore, the melting phenomena of spheroidal graphite cast iron is changed by the existence of steadite. 2. In spheroidal graphite cast iron containing little phospher, melt appears first at the outer region of austenite shell in which Si is condensed, regardless of heating rate. In this case, grain boundaries in austenite shell give little effect on the melting procedure of spheroidal graphite. 3. In spheroidal graphite cast iron containing phosphor above 0.3%, melt appears first along the interface between spheroidal graphite and austenite shell, at low heating rate. It seems to be caused by moving of liquid phase to spheroidal graphite along grain boundaries in austenite shell. But, at high heating rate, melting proceeds with remaining austenite shell around spheroidal graphite.

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Magnetic properties and secondary recrystallization of high permeability 3% silicon-iron alloys containing boron, sulfur, nitrogen and various amounts of MnS have been studied as a function of final cold reduction using two stage cold rolling method. The results show that the optimum final cold reduction to be 80-85% for boron-silicon steel with small amount of MnS and 60% for boron-silicon steel with large amount of MnS (0.12 w/o Mn). It was found that edge cracks during cold rolling decrease as the amount of MnS increases and that the maximum B_(8) also decreases with increasing MnS.

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The hydrogen Thermal Analysis experiments have been carried out for the identification of hydrogen trapping character by nonmetallic inclusions in AISI 5160 spring steel. It was found that oxide inclusions including Fe-oxide, Al₂O₃and SiO₂have a strong interaction with hydrogen relative to the other defects such as the cementite-ferrite interfaces and microvoids. Also, the trap activation energies of hydrogen for each inclusion were determined as follows. They are 50.6 kJ/mole and 69.5 kJ/mole for the Fe-oxides like Fe₃O₄, and Fe₂O₃, 86.2 kJ/mole for the Al₂O₃and 112.1 kJ/mole for the SiO₂respectively. The thermal analysis technique could be used to predict the fatigue properties of the steel by identifying the nonmetallic inclusions and determining the amount of them in the steel.

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