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Mechanical properties, metallurgical structures and fiber textures of Cu-Fe alloys were investigated and the following results were obtained.(1) The quenched Cu-Fe alloys are harder than the slowly cooled Cu-Fe alloys after holding at the temperature range over the eutectic point, and the faster the cooling rate is, the larger the difference of hardness becomes.(2) Cu-Fe alloys subjected to severe cold drawing come to have fine fibrous structures. On the said occasion the Fe-rich phases have strong α fiber texture, but the Cu-rich phases only have weak e fiber texture.(3) When the specimens are annealed at 800°C below the eutectic point, the Cu-rich phases recrystallize and come to have strong e fiber texture even before the recovery of the elongation. On the other hand the Fe-rich phases grow in size with the lapse of time. When they reach to a certain size, the elongation also reaches to a certain amount. The growth of the Fe-rich phases are in good accordance with the recovery of the elongation.

Metallurgical structures and ductile fracture surfaces of spheroidized carbon steels and quenched and tempered steels were investigated and following results were obtained.1) The fibrous rupture surfaces of tensile specimens of steels used were, micro-fractographically, consisted of dimples. Among them, in the center of rupture surface, they were “equi-axed” dimple.2) The dimple size was found to distribute as “logarithmically normal distribution” and in the large dimple, second phase particle or its trace was observed. On the other hand, in the small dimple any particle or its trace was not observed. So, in this paper, we call temporarily the former “primary dimple” and the latter “secondary dimple”3) The depth of dimple was observed to be about 1.0 or 1.5 times the diameter of dimple, but it is more reasonable to suggest dimple to be funnel shape, so the ratio of the depth of dimple to the diameter will be larger than the value mentioned above.4) A close correlation between the dimple size and the mean free ferrite path of spheroidized carbon steel was found, but any relation between some kinds of metallurgical factors of quenched and tempered steel and dimple size was not observed.5) On the basis of the existence of primary dimple and secondary dimple, a ductile rupture model was presented that primary dimple corresponds to the void nucleated around a second particle before rupture and secondary dimple will be formed when unstable fracture occurs between neighboring primary dimples at final rupture.

Solution and precipitation characteristics of vanadium compound during isothermal heating and during some heat treatments such as isothermal transformation, continuous cooling transformation, tempering and so forth in carbon steel, Mn steel, Mn-Cr steel, Mn-Cr-Mo steel bearing 0.15% vanadium was investigated. Furthermore, the role of vanadium compound on the changes in mechanical properties and microstructure due to quenching followed by tempering was also investigated, and following results were obtained;1) Solid soluted vanadium precipitates during reheating, and the amount of precipitation makes maximum at 800°C. Vanadium compound solutes into matrix almost completely at 1100°C. The addition of about 1% of Mn, Cr, and Mo has no influence on above mentioned precipitation and solution characteristics of vanadium compound.2) Vanadium compound precipitates during isothermal transformation and continuous cooling transformation of austenite, and under the suitable condition of transformation, it has coherency with matrix and harden ferrite. In case of continuous cooling transformation, the most adequate cooling velocity to harden matrix has relation with hardenability, namely precipitation behavior of protectoid ferrite.3) The effect of vanadium on the hardenability is found at far from quenched end, where protectoid ferrite exists.4) The difference of strengthening mechanism between vanadium bearing steels and other steels subjected to high temperature tempering are found that the contribution of precipitation itself of vanadium is much more than that of retardation of recrystallization (and high dislocation dencity) due to precipitation of vanadium.

The dissolving behavior of the carbide of 21-4N steel for exhaust valves in solution-treatment and precipitation behavior under aging have been investigated. Furthermore, the mechanical properties of 21-4N steel which shows remarkably different micro-structures despite of similar age hardness was also examined.The hardness, the amount of undissolved carbide, grain size number and lattice parameters of matrix after solution-treatment are found to be adjusted by heating condition: parameter P=(T+475.32)×(logt+38.398), (T; °C, t; hr) and the amount of the main undissolved carbide M23C6 exerted considerable influence on age hardenability.The amount of nodule fraction of grain boundary reaction after aging depends upon the condition of solution-treatment and the maximum age hardness could be obtained under the treating condition where comparatively slight nodule fraction of grain boundary reaction generates.After comparing the test piece treated as hard as HRC37 which has fine grain and much amount of nodule fraction of grain boundary reaction with the test piece of coarse and uniform grain having little nodule fraction of grain boundary reaction concerning their mechanical properties, it was confirmed that the latter is superior to the former regarding tensile strength, impact value, fatigue strength and creep-rupture strength, but no difference was recognized between the former and the latter about corrosion resistance to various molten ash.

鋼材は目的に応じて各種の熱履歴を経て使用される。Tiを含有する鋼に不適当な熱履歴を施した場合には焼入れ焼もどし後の機械的性質の劣化する現象が認められた。含Ti鋼における機械的性質の熱履歴依存性を究明するため,機械的性質,金属組織,変態特性,Ti炭化物の析出挙動に対する低温,高温熱履歴の影響を調べたところ,低温熱履歴現象は低温焼なましの際に析出したTi系炭化物が再加熱時にオーステナイト結晶粒を微細化したために起こる焼入性の低下によるものであること,高温熱履歴現象は高温加熱の際に生地鉄中に溶け込んだTiが再加熱時に旧マルテンサイト粒界に析出したことによって生ずるAc3変態点の上昇によって説明できることがわかった。

So far, it has been said that the ductility of metal containing hard particles depends only on the volume fraction of particles, f, and the ductility decreases with the increase of f. On the other hand, according to engineering experiences, it is well known about, at least, spheroidal carbon steels, that the larger cementite size, the better cold formability of it. Therefore, the purpose of this work is to investigate the influence of not only the amount of spheroidal cementite particles, but also, especially, the cementite particle size on the strength and ductility of spheroidized carbon steels. And the relationships between structural factors and work hardening charcteristics, rupture strength, rupture surface appearances and so on were studied, and the following results were obtained;(1) Work hardening characteristics coincides, on the whole, with the theory presented already, but power number of f/(1-f)d is about 0.20.(2) The amounts of strain before rupture, including almost from 10% of rupture strain corresponding to strain at the onset of local necking to 80% of rupture strain, have relation to work hardening rate, that is, the more work hardening rate, the less strain before rupture.(3) The contribution of spheroidal carbide size to rupture ductility is found to be little but distinct, and the bigger carbide size, the more rupture ductility.(4) Mean diameter of dimples of ruptured surface is about 1.5 or 2 times ‘true’ mean free ferrite path in the range of experiment.(5) The tensile fracture stress at the longitudinal axis of specimen increase with the decrease of d and f. Furthermore, the results (1), (3), (5), mentioned above, were expressed as experimental equations.