발간논문

Home > KJMM 논문 > 발간논문

The present paper is concerned with the basic study on the degree of normalization in spheroidal graphite cast iron. The tensile strength, hardness and elongation of as cast specimens are compared with the standard sample`s and the results obtained in this study are as follows; 1. The tensile strength of standard type is expressed as following equation. σ_i=15.6Sc+30.9 2. The degree of normalization in spheroidal graphite cast iron is 144% when the diameter of sample is 20㎜ and Sc=1. 3. The normalized hardness in spheroidal graphite cast iron is 1.49 when Sc=1. 4. The normalized elongation in spheroidal graphite cast iron is 0.46 when Sc=1.

keyword :

The surface tensions of Pb, Sn, Pb-Sn binary alloys and Pb-Sn-Sb ternary alloys have been measured by the sessile drop method in the range of temperatures from the liquidus temperature to about 550℃. Within the limits of experimental error, the surface tensions of Pb-Sn alloys are in good agreement with those of past works. These values decreases linearly with increasing temperature and the temperature coefficient of the surface tension -dγ/ dT has a minimum in the vicinity of the eutectic composition. This anomalous behaviour has the relation of the preferential adsorption of Po in the surface phase. The change in the surface tension of Pb-Sn alloys with composition agrees with the equations for the regular solution model derived from statistical thermodynamic considerations. The surface tensions of the ternary alloys (40%Pb-60%Sn+Sb) have been determined and the addition of antimony reduces the surface tension of Pb-Sn alloys.

keyword :

The author studied, according to each heat-treatment structure, the effects which the amount of nickel gives to the toughness in the low-alloy steel of tough-hardening steel of Ni-Cr-Mo. For the comparison of toughness, each fracture toughness was compared with one another, using side notched test-pieces with pre-crack from fatigue and the fracture surfaces were observed. The important results obtained are as follows. 1. The amount of nickel has an effect to arrest the propagation of fracture-crack, independent upon the heat-treatment structure. 2. Intermediate structure that consists mainly of bainite is inferior to tempered martensitic structure in mechanical quality both of strength and toughness. 3. When low alloy steel of Ni-Cr-Mo undergoes isothermal transformation treatment for long hours, its toughness becomes inferior, however continuous cooling transformation structure becomes tough and its mechanical quality superior.

keyword :

The precipitation sequence and the variation with time and temperature in the growth rate of the rod-like aluminum nitride precipitate were investigated for an Fe-AI-N alloy. Using an extraction replica technique, face centered cubic aluminum nitride was observed at the initial stages of precipitation, and this later transformed into the rod-like hexagonal close packed aluminum nitride. The amount of aluminum nitride was closely related to the grain size; that is, the greater the amount of aluminum nitride, the smaller the grain size. The mean volume ratio of the precipitate is nearly proportional to the square root of the concentration product of aluminum and nitrogen contents. At a given temperature, the length of the rod-like precipitate was proportional to the holding time, and the diameter of the precipitate to the square root of the holding time. The orientation relationship between the rod-like aluminum nitride and the matrix has been determined by means of transmission electron microscopy. It gives (001)p∥(001)ｍ 〔001〕p∥〔2―10〕ｍ

keyword :

This study was concentrated on the experimentally measurable factors which affect the iron precipitation as Jarosite from ferric sulfate solutions. Of seeding quantity, alkali ions, the pH value and temperature, the seeding addition increased the initial rate of iron precipitation and the pH was found to have the greatest effect on the precipitation reaction. To expedite the precipitation of iron as Jarosite during the reaction, the constant pH value of 1.5 was the most preferable. The experimental rate expression for the iron precipitation as Jarosite was as follows: 1/[Fe]²-1/[Fe]²_0=2Kt The activation energy for the reaction was found to be 18Kcal/mole.

keyword :

keyword :

keyword :

keyword :

keyword :

keyword :