The combustion method has an important effect upon the efficieney of heating and melting operation, especially the practice of open hearth furnaces is seriously influenced by it. Formerly the mixed combustion of low-pressure coke-oven-gas and liquid fuel had been used, and the authors, making research on a better combustion method, reached to the conclusion after some experiments that high-pressure coke-oven-gas flame would be more advantageous for melting operation, and this high-pressure coke-oven-gas combustion was put into practice. The authors studied on the relation between flame length, temperature, pressure and a melting test with the high-pressure coke-oven-gas (about 1kg/cmcm2) in the model open hearth furnace. The results obtained were as follows. i) Actual velocity (Va) reached constant value at about 1kg/cmcm2 burner pressure. ii) The higher the burner pressnre, the longer the flame length. iii) Average flame temperature was corresponding to the burner pressure. iv) At about 0.7kg/cmcm2 burner pressure, cutting effect becomes stronger. v) Momentum flux was saturated with the 50mm φ burner at 4000Nm3/h.
Amethod suitable to measure electrical conductivity of molten slags in the nitrogen atmosphere at temperature as high as 1450°C, using pure iron as the crucible and the electrode, was described. In order to eliminate leads resistance the "four-terminal method" was applied. By this method the eleCtrical cohductivity of the FeO-TiO2 system was measured in the temperature range of 1450-1200°C. The specfic electrical conductilvity was 30-300Ω-1cm-1, which was very high as compared with the conductivity of ordinary ionic condgctors. The change of conductivity with temperature in molten state was very small. For the range of high TiO2 contents in the conductivity-ternperature curve an anomalous change appeared in the neighbourhood of the solidifying temperature, which was peculiar to the slags of high TiO2-contents. Though conductivities could not be measured in the continuous range of composition owing to the high melting point, it was shown that the conductivity decreased with increase of TiO2 in the range of TiO2 contents less than about 40 mol%, beyond which the conduc-tivity increased with enhancement of TiO2. Both FeO and TiO2 are semi-conductors and a semilar mechanism of semi-conduction might be predominant in the FeO-TiO2 system. In the range of low TiO2 contents the high conductivity was ascribed to semi-conduction concerning. Fe ions, while at the high TiO2 contents the main part in conduction was played by electrons belonging to Ti ions. The probable forms of ions are presumed to be Fe++, Ti4+ and O--, contrary to TiO44- and TiO32- as assumed by O.A. Esin etc.
The microscopic structure and chemical composition of streak seams in the experimentally prepared 5 ton killed steel-ingot (200-500g/t Al were added) were investigated, then the mechanism or process of the seams-occurrence were researched. The results obtained were as follows. (i) Mn-silicate type of seams found very rarely in the bottom or surface of the ingots were the reaction-products between refractory materials and [Mn], [MnO] or [Fe]. (ii) Al2O3 type-seams found in the interior of ingots were almost Al2O3 crystal and high Al2O3 type-seams containing 65-70% Al2O3 had Al2O3 crystals precipitated on the matrix of Mn-Fe-Al-silicate. (iii) Al2O3 type and high Al2O3 type-seams originated from the oxidation of [Al] by the air and the reduction of eroded refractory particle by [Al]. (iv) Al2O3 type and high Al2O3 type-seams already grew in the metals of runner brick at the hottom pouring. They happened in the narrow metal independently of the theories of the cedimental crystal or the segregation at ring ghost in the large ingot. (v) The maximum length of the seams coagulated by the effect of cedimental crystal were calculated under some assumptions. They wese about 2-3mm when the forging ratio of ingots were 10-20. But by the observation of seams-distribution in ingot, the effect of cedimental crystal was rather thought to prevent the floating up of the macro-scopic inclusions in the mold. The effect of the cooling velocity of mold-bottom on the floating up of macroscopic inclusions poured into the mold (top poured), the relation between the demension of the ladle or nozzle and the poured stream-condition of molten steel and so on are now being studied.
Creep is considered to appear as the result of deformation of crystal grains and movements at crystal boundaries; but, as the effect of the latter is secondary and its theore- tical treatment is very difficult, it may be disregarded in the first approximation. In this report, adopting the effect of dislocation in crystal in qualitative meaning, the author defines the rate of work-hardening as the mutual reaction of dislocations and represents the usual experimental formula of creep as the function of stress and rate of work-hardening. He discusses the stationary state of creep as the application of this theory, and describes the rapid method of measuring the creep rate of the stationary state.
The influence of the nitrogen (0.04-0.16%), degree of working (0-30%), and the solution-treatment temperature (1200°, 1250°C) on the high-temperature age-hardening of Timken 16-25-6 heat-resisting alloy were studied. The results were summarized as follows. (1) The hardness increased almost linearly by the cold working (0-30%) but had little difference by the nitrogen content. (2) The age-hardening at 600°C was not nearly influenced by the nitrogen content and the effect of the degree of working was somewhat greater than the effect of the solution-treatment temperature. In the case of aging at 700°C, the increase of hardness was remakable and the solution- treatment temperature was effective much greater than the degree of worklng, and the higher the solution-treatment temperature was, the more became the increase of hardness. On the contrary the higher the nitrogen content was, the smaller became the increase of hardness. The increase of hardness at 800°C was smaller than that at 700°C and the influence of nitrogen at 800°C was similar to that at 700°C. (3) In regard to the influence of the degree of workeing on the increase of hardness, in the case of aging at 600°C, the increase of hardness decreased little according to increase of working, and in the case of aging at 700°C the maximum increase was obtained by the working at 5-10%. In the case of aging at 800°C, the increase of hardness decreased linearly according to increase of working and at the degree of working above 20% softening arose. (4) In the microstructure, the working accelerated the precipitation and the precipitate reaction became 4-5 times by the 5% working. The greater the degree of working was, the more became the quantity of precipitates, and the more homogenious the distribution of precipitates. Generally the smaller the nitrogen coatent was, the faster became the coagulation of the precipitated particles. (5) In the tempering at 500-1100°C of cold worked (0-50%) materials, the more the degree of working was, the lower became the temperature at which the maximum hardness obtained. In the case of tempering at 500-1100°C of 26% cold worked materials, the higher the nitrogen content was, the slower became the decrease of hardness.
The influences of added C, Mo, and N contents on precipitation hardening were investi-gated. There were 23 kinds of samples with varying chemical composition of C, Mo, and N. For the purpose of studying the influence of varied contents of added elements on precipitation hardening, 13 group were made by various combinations of all samples. After hot forging to bars, all samples were solution treated at 1200°C for 1 hour. Then, they were aged at 800°C up to 150 hours. Hardening was measured by hardness at 1, 3, 15, 30, 50, 75, 100, and 150 hours. And, the microstructure of such aged samples was also observed. It was concluded from this experiments as follows; (1) Carbon contents had more remarkable influences on precipitation hardening than Mo or N contents. If the carbon contents increased, hardness was raised and phenomena of double peaks on hardening process became more evident. (2) Although influence of Mo contents was not found immediately after solution treatment, more Mo meant more hardening when it was aged at 800°C. If Mo content was much less than 6%, softening was indicated after 150 hours aging at 800°C. (3) In the experiment of Reports (IX), the influence of N content on precipitation hardening was not apparent. This was already investigated in Reports (V) in much more details.
The author analysed the quantjty of retained austenite employing the integrated intensity of X ray diffraction lines and Hurlbut counter to quantify the results of dimensional stability of ball bearing steel mentioned in Report No.1 and 2. The results were as follows: 1) The retained austenite increased with higher quenching temperature, and repeated quenching increased it too. 2) The retained austenite increased by tempering immediately after quenching. 3) The retained austenite.decreased about 3-4% by one day of air cooling after quenching and prior to tempering, or by employing secondary tempering, compared with specimens tempered immediately after quenching. 4) The retained austenite decreased by subzero treatment and even after marquenching. 5) The quantity of spheroidized carbide decreased by higher quenching temperature and also by repeated quenching. 6) The crystal structure before quenching affects the diffusion of spheroidized carbide into matrix. Increase of the retained austenite was proportional to the degree of spheroidized carbide diffusion into matrix. The dimensional stability was also influenced by the crystal structure. 7) The quantity of retained austenite was influenced by the cooling rate according to the mass of specimens. The above results can quantitatively prove the experiments on dimensional stability of ball bearing steel introduced by the previous two reports. Moreover, he studied relations between the .dimensional changes by heat treatment and the retained austenite and magnetic properties, for further considerations on ball-bearing steel problems.
Lately, some chromium-molybdenium-vanadium tool steel for hot work such as drawing of copper, brass and aluminum pipes or angles are used in Europe and America. A series of experiments were carried out to study transformation point of some Cr-Mo-V tool steels, and afterward, hardness and rate of deformation of samples subjected to different heat treatments were measured. And then, as the tool steel was used for hot work, changes in hardness and impact value at high temperature were also observed. Moreover, the authors carried out the comparison with W-Cr-V tool steels which had been used hitherto, and ascertained the optimum heat treatment of some Cr-Mo-V tool steels tested in this investigation.
The MK permanent magnet Fe-Ni-Al ternary aloy was invented by Tokushichi Mishima (one of authors) in 1930. Since then the magnetic properties of this alloy underwent no mprovement to a remarkable degree for sometime. During the 2nd World War, it was disgovered that MK magnet containing the certain restricted range of comnosition could attain to excellent magnetic properties by the heat-treatment in magnetic field. In our country, the investigation of the magnetic treatment of MK magnet was kept on for a long time in Mishima's laboratory in University of Tokyo. In this report, the results of such investigation on the effects of chemical composition and additional elements on the magnetic properties of this anisotropic Mk magnet alloy will be described. The experimental results on the heat-treatment and industrial aspects mav be reported later. Briefly this report may be summarized as follows: According to the increase of Ni content up to 17%, the coercive force is improved, but the residual induction be omes inferior. Increase of Co content up to 28% is preferable for the residual induction, but its content is relative to Ni content and it is desirable to restrict the total content of Ni and Co to 38 or 39%. The magnetic properties is sensitive to Al content. The optimum composition is 7.8-8.4% and unfavourable effects become marked when Al contents reach to less than 7%. The optimum chemical composition of Al needs to be changed according to the additional Si and Ti contents. C content has to be kept under 0.05%, because it is apt to cause a remarkable deterioration of the magnetic properties. Addition of Ti is effective in overcoming its undesirable effects. As Si, Mn and P ill-effect on the magnetic properties, it is advisable that Si, Mn and P contents should be kept respectively lower than 0.2%, 0.3% and 0.02%. Addition of Cb and Zr is favourable to the magnetic properties, especially Cb is effective to improve the coercive force. The effects of other additional elements: B, Cr, W, Mo, V, Be and Sn, is unpreferable to the magnetic properties.