발간논문

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Interdiffusion coefficients of manganese D～ were investigated as the functions of solute atom of Mn in FCC-γ phase of Fe-Mn-C ternary alloy at 950℃ and 1000℃ by using the vapour-solid couple method. D～ are gradually increased by the addition of Mn and the values are in the range of D～=0.040-0.240x10^(-10)㎠/s. Diffusion of Mn atoms are accelerated in the matrix which has contained C atoms, but the increment in D～_(Mn) with increasing Mn concentration is lessened in the matrix which has contained C and Mn atoms. In order to study the intrinsic diffusion phenomena, the diffusivity of Mn atoms D_(Mn) were calculated by the equation of Darken and Manning with the thermodynamic factor and structure factor. The difference between D～_(Mn) and D were in the range of 10-40%, and it`s tendency was increased with the concentration of Mn.

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For the purpose of low energy and stable operation in the blast furnace, physical and chemical properties on iron ore sinter of low SiO₂ and FeO were investigated. The results obtained are summarized as follows: 1) With the decrease of FeO content in sinter under the same basicity, reduction degradation rate at 550℃ and reduction rate at 900℃ were improved. 2) The more quantity of skeletal hematite shows the worse effect on degradation of sinter under the reduction atmosphere at 550℃. 3) With the decrease of SiO₂ content in sinter under constant basicity and FeO, reduction rate at 900℃ and shatter strength are improved, while reduction degradation rate at 550℃ are not improved.

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Experiments were carried out to investigate the effects of various casting methods and ESR, together with the addition of 2% nickel and 1% tin on the structure and wear properties of Cu-Pb alloy. The results obtained are as follows; 1) Inter-rod spacing of lead in ESR ingot was inversely proportional to the square root of solidification rate. 2) Wear resistivity of ESR ingot was superior to that by sand castings or chill castings. 3) Wear mechanism of Cu-Pb alloy seemed to be metallic and melting wear, no oxidizing wear was appreciable. Therefore, wear amount increased with increasing sliding speed.

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Effect of transformed ferrite content on the mechanical properies of dual-phase steels has been studied and analyzed on the basis of observation on the austenite-to-ferrite transformation behavior during post-anneal cooling. Various contents of transformed ferrite were obtained by changing intercritical annealing temperature. As the transformed ferrite content was increased up to about 40%, dual-phase properties became better due to the finer distribution of martensite particles. However, the dual-phase properties were deteriorated when the transformed ferrite content becomes larger than the retained ferrite content. The significance of these results is discussed in relation to the austinite-to-ferrite trans formation behavior during intercritical annealing.

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Tensile properties and fracture behavior of AISI 4340 steel have been measured as a function of tempering temperature from 200℃ to 600℃ and measured direction. The tensile and yield strengths, and the hardness of specimens decreased with increasing tempering temperature and these did not vary much with test direction, whereas the ductility and toughness increased with tempering temperature. The reduction ratio in rolling direction had the higher value compared with that in transverse direction, the charpy impact value and the fracture toughness increased with increasing tempering temperature, the properties in the rolling direction were superior to those in the transverse direction, and the relation between K_(IC) and CVN values showed (K_(IC)/σ ys)² = 0.382 (CVN/σ ys+0.01) in the rolling direction and (K_(IC)/σ ys)²= 0.582 (CVN/σ ys-0.000054) in the transverse direction.

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Quaternary systems Cu-As-Ni (Co, Fe)-S with Au or Pt were studied at 1200℃ for Au and Pt distribution between matte and speiss. 1) Au or Pt exists almost in speiss. The content of Au or Pt in speiss is increased with the Cu content (except Cu content as Cu₂S) in speiss. 2) Pt distribution in the quatenary systems has similar trend to that of Au. The ratio of distribution coefficient of Au or Pt (K_(Au) or K_(Pt)), which is defined as the ratio of weight percentage of the noble metals in matte to that in speiss, can be expressed as follow: K_(Pt):K_(Au):K_(Ag)=1:10:50. 3) The effect of Ni on Au solubility in speiss is not same as that of Co or Fe, because Ni forms solid solution with Au in all composition range.

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While a forecast of world demand for steel from the latter half of 1980s through to the year 2,000 is attempted, problems facing steel industries in developed countries are analyzed. Three scenarios for world steel trade are presented. With a review of the present status of steel technologies in developed countries, their forecast through to the year 2,000 is undertaken. Finally, in order to steer the development course of the Korean steel industry as close as that of the most desirable, problems of how to set objectives for technology development, of what guidelines to be followed for technology development activities, and of what R & D system to follow have been studied, leading to more concrete suggestions for development strategy of the steel industry.

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