低温脆性に関する二, 三の実験

概要

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The author investigated the effect of heat treatments (quenching and tempering, normalizing, annealing and etc.) on low temperature impact resistance of pure irons and mild steels.The structure of pure iron as quenched into water had the higher energy value at low temperature and the lower mean energy transition temperature than the annealed one.The quenched and tempered structure of mild steel had the highest energy value at low temperature and the lowest mean energy transition temperature. The annealed structure of mild steel had the lowest energy value at low temperature and the highest mean energy transition temperature.It was found that the structure of mild steel as quenched into water has the lower energy value at +25℃, 0℃, -20℃ than the annealed structure and the structure as rolled, but on the contrary had the higher energy value at -40℃ and -60℃.The author concluded that the impact resistance at low temperature depends upon the grain size of ferrite.The microstructures of pure iron and steel were examined by means of the electron microscope at 25℃, -30℃ and -80℃. It was found that there were no difference in these structures.The author investigated on the electron diffraction figures of iron and steel respectively at +25℃, -30℃ and -80℃, and found that the spectrum lines of these specimens were diffused at low temperature.