Tetsu-to-Hagané
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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 43 (1957), No. 10

  • STUDY ON THE PRESSURE LOSS AND HEAT-TRANSFER IN THE PACKED COLUMN FROM THE METALLURGICAL STANDPOINT

    pp. 1089-1093

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    The pressure loss and heat-transfer in the packed column were studied at elevated temperatures. In spite of many investigations most of their results were based on comparatively low temperature experiments relating chemical industries.
    The authors found that their results were hardly available for elevated temperature fluid (more than 300°C mean temperature) and obtained experimental formulas available for the fluid of 300°C, 450°C and room temperature. Air was used as the flowing fluid and magnesia clinker as packed material. The authors' formulas were led from the results of dimensional analysis and could apply 40-500 Reynolds number. Heat-transfer in the packed column at elevated temperaby use tures was analysed of Kuzuoka's equation that had already reported.
  • AERODYNAMIC CONSTITUTION OF OPEN-HEARTH FURNACE (VII)

    pp. 1094-1098

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    The burner jet is an important constituent of the open-hearth furnace. It has to induce a favourable flow, in harmony with the uptake flow and the space of the furnace, and to compose the rational mechanism of combustion.
    Model studies on the arrangement and the functions of the burner jet explained followings:
    (1) The inserting length of the burner is appropriate to be a quarter of the chamber width.
    (2) The setting height of the burner is 30% of the chamber width and its inclination is 12°.
    (3) The burner direction affects largely and sensitively the combustion and the wear of the furnace.
    (4) The combustion is controlled by changing the quantity of the atomizing agent or uptake air.
    (5) The intensities and the directions of the twin burner jets have large effect on the furnace flow, the flame lengths of the twin jets are shortened by increasing the jet fluxes and slight convergence of the burner directions.
  • STUDY ON INGOT-MAKING PRACTICE (V)

    pp. 1098-1104

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    The non-metallic inclusion in steel is greatly influenced with oxidation of molten steel by air during pit-practice. The authors studied on oxidation of various elements in molten steel during pouring and effect of casting conditions on oxidation.
    The results obtained were as follows:
    1. Silicon, manganese, aluminium and chrome were oxidized in proportion to content of these elements before pouring.
    2. Increased SiO2 and MnO in steel during pouring were about 3-% and 7-15% of total amount of oxidized silicon and manganese respectively.
    3. Increased Al2O3 was about 25% of total amount of oxidized aluminium and it was correspond with about 50% of total Al2O3 in steel after pouring.
    4. Oxidation of chrome was not oxidized strongly in comparison with the other elements, but increased Cr2O3 during pouring was correspond with about 50-100% of total Cr2O3 in steel after pouring.
    5. The molten steel of slow casting velocity was more oxidized heavily than the case of fast casting velocity.
    The oxidation of molton steel by air during pouring was influenced with the condition of its stream.
  • SOME STUDIES ON SEMI-KILLED STEEL (I)

    pp. 1104-1110

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    A number of test ingots weighing about 4 tons were made of semi-killed Steel of C: 0.16-0.25% and Mn: 0.34-0.54% by applying widely different degrees of deoxidation. Taking a test-piece from the corner of each of these ingots, an investigation was carried out of the conditions of blow-holes: the relations between the degree of deoxidation and the number, the size, the position and the distribution of blow-holes were tried to be nade clear.
    Further, a study was made also about the mechanism of blow-hole formation. After studying quantitatively the roles of CO, H2 and N2 to be played about formation of blow-holes, it was concluded that in case of semi-killed steel, no small care must be paid not only to the degree of deoxidation, but also to H% in moltem steel, inasmuch as that the stronger the degree of deoxidation becomes, the more the CO% in the composition of gas will get decreased, and when the deoxidation is raised so much that almost no blow-holes will come about, the gas composition will be CO: about 30%, H2: about 60%, N2: about 10%.
  • STUDIES ON THE INGOT MAKING PROCESS IN NITROGEN ATMOSPHER (II)

    pp. 1111-1122

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    Following the previous paper, Tetsu-to-Hagané vol, 42 (1956) No. 10, p. 956-961, some experimeats are achieved on the nitrogen-blowing process. Results obtained are summarized as follows:
    1) Surface appearances of rolled billets: Surface appearances of rolled billets made by the nitrogen-blowing process are superior to those by the ordinary and floating boards processes.
    2) Appearances of sub-surface defects of rolled billets: Appearances of sub-surface defects of rolled billets by the nitrogen-blowing and floating boards processes are both clean. Applying the nitrogen-blowing process, the surface appearances of rolled billets are clean and the sub-surface defects don't occur, so that the mold dressings are unnecessary.
    3) Gas contents in inside and outside parts of rolled billets, -oxygen and nitrogen: Oxygen contents of rolled billets are nearly equal between the nitrogen-blowing process and the ordinary one. Sand contents of rolled billets made by the nitrogen-blowing process are somewhat lower than those by the ordinary process. However, this point must be checked by the abovementioned sampling methods, analytical methods and ingot size. Nitrogen contents of rolled billets are nearly equal between the nitrogen-blowing and ordinary processes.
    4) Cleanliness and grain size in inside and outside parts of rolled billets; Cleanliness of rolled billets by the nitrogen-blowing process are better than the ordinary one. Grain size of rolled billets are nearly equal between the nitrogen-blowing and ordinary pyocesses.
    5) Effects of nitrogen on the properties of finished products: Effects of nitrogen on the properties of finished products must not be considered, because nitrogen contents of rolled billets made by the nitrogen-blowing process are nearly equal to other processes.
    Following the above mentioned experiments, some theoretical considerations on the nitrogenblowing process are achieved as follows:
    1) Oxidation of molten steel by the atmosphere in mold;
    2) Beginning temperature of oxidation for active elements in molten steel
    3) Nitrogen absorption of molten steel.
  • EFFECT OF HOT WORKING ON GROWTH CHARACTERISTICS OF AUSTENITE GRAINS IN STEEL

    pp. 1122-1127

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    For medium-carbon steels and a medium carbon Cr-Mo steel having different grain size, the effect of hot working on growth characteristics of austenite grains was studied by changing the forging ratio from 2 to 10.
    From this work, it was concluded that hot working lowered the coarsening temperature of austenite and that annealing after forging much lowered it. These were more clearly observed in a duplex-grained steel than in a fine-grained steel. It was also found that the effect of hot working and annealing on coarsening temperature was much smaller than that of the difference of ingot size. It was veritied, therefore, difference of grain size and grain growth characteristics between a ladle sample and a finished product was mainly due to the difference of teeming conditions.
    Moreover, taking account of the behavior of AlN in steels, it was deduced that the effect of hot-working and annealing was the function of the state of aggregation of AlN and the occurrence of duplex grain structure, detected in this work, in as-forged state was also related to the behavior of AlN in austenite.
  • STUDIES ON MECHANICAL PROPERTIES OF TIMKEN 16-25-6 AT ELEVATED TEMPERATURES (V)

    pp. 1127-1131

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    The authors studied the mechanical properties of four turbine rotors of Timken 16-25-6, to compare with that of the forged bars, of which they reported already. The results were as follows:
    1. The effects of heat treatment on mechanical properties in the turbine rotors are the same as the forged bars. The "hot-cold worked" rotors have higher strength than the preci-pitation-hardened rotors.
    2. The "hot-cold worked" rotors have the similar or somewhat lower value of the creep rupture strength and tensile and proof strength as compared with the forged bars. The rotor which have sufficient forging effects, have great ductilities and uniformity of mechanical properties.
    3. The precipitation-hardened rotors have nearly the same mechanical properties when compared with the forged bars.
    4. When forging effect of the rotor are insufficient, the clear pattern of micro-segregation are recognized, so that the ductilities are low and not uniform.
    5. The mechanical properties of specimens which are taken in tangential or radial directions from the boss part of the upset rotor are lower in ductility than that taken from the rim part of rotors. It is because of the metal flow of the boss part that is across with the tensile direction.
  • STUDY OF HEAT-RESISTING STEEL (XII)

    pp. 1132-1136

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    The study of Timken 16-25-6 alloy containg Ti or B was reported in the report (X) (XI) (Tetsu-to-Hagané vol. 43, 1957, No. 5. p. 543-550, No. 7, p. 713-720) of "Study of Heat-Resisting Steel". The report (X) explained precipitation-hardening phenomena of the above alloy. In the report (XI), warm work effect on 16-25-6 alloy containing Ti or B was determined. In this report, the creep test at 650°C was made.
    There were four samples with different chemical components. Sample #D5 contained 1.3% Ti, #D6 contained 0.060% B, #D7 contained 0.08% Ti and 0.025% B, and #B11 was standard Timken 16-25-6 that contained 0.13% N. After hot forging, they were solution-treated at 1150°C for 1 hour, and aged at 800°C for 50 hours. After this treatment, samples of measurements for the creep test specimens were machined.
    Creep test was made at 650°C for 500 hours with a load of 18kg/mmmm2. Then, each specimen was examined for hardness and observed through a microscope.
    Sample #D5, 16-25-6 alloy containing Ti, showed remarkable higher creep resisting properties than standard 16-25-6 alloy and other samples. Standard 16-25-6 alloy, #B11, and sample #D6 showed similar creep curves. Sample #D7 was rather weaker than #B11 and #D6. It was concluded that the addition of Ti effected creep strength; and the addition of B instead of the usual N may prove desirable to keep creep strength at the standard level. But, addition of a small amount of Ti and B was not so effective.
    In this report, other age-hardening phenomena in sample #D5, for example, soaked at 650°C after aged at 800°C, was also described.
  • AUSTENITIZING BEHAVIOUR AND RAPID LIFE TEST OF DRAWN WIRE FOR BEARING BALLS

    pp. 1137-1142

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    In this report, austenitizing behaviour and rapid life test of drawn wire for bearing ball were studied, and the effects of ingot size's difference, raw materials and vanadium addition were investigated.
    The results obtained are summarized as follows;
    (1) In quenching and tempered (1h) condition, the hardness increases to 860°C quenching temperature, but above 860°C it decreases.
    (2) The bending stress decreases generally with quenching temperature, and between 820°C and 840°C quenching temperature it does not decrease except B steels.
    (3) The solution of the carbide into austenite is very rapid to 840°C temperature, but inactive above 840°C temperature.
    The austenitizing behaviour of the carbide is very different in C 1 and C 2 on account of vanadium addition.
    (4) In A steels the retained austenite increases with quenching temperature, and it does not increase to 840°C quenching temperature in C steels.
    (5) In rapid life test of A steels the mean and standard deviation of life times become better and crack damage is improved, if the imported scraps from america are charged more as raw materials.
    The mean of it becomes better, but crack damage becomes worse on account of vanadium addition in C Steels.
    In commercial B steel the mean of it and crack damage are worst.
  • ON THE HOT STAGE MICROSCOPY -AREVIEW-

    pp. 1143-1152

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    The history of progress and application of the hot-stage microscope were reviewed. Moreover its application in future was mentioned. A new type hot-stage microscope with 16mm cine camera developed by the authors was reported, and photomicrographs of the martensite and bainite transformation of Ni-Cr-Mo steel were explained.
    By analysis of the film, it was observed that the martensite needles were formed abruptly at Ms point and successively with decreasing temperatures; the bainite needles nucleated and grew isothermally at transformation temperature.
    The martensite transformation was the athermal "Umklappung" transformation by the shear process. And the bainite transformation proceeded with the nucleation rate and the coherent growth rate which depended on the transformation temperature. It seems that the growth rate of bainite needle was controlled by the diffusion rate of carbon.
    The vacuum heating stage with loading mechanism was also manufactured by way of experiment, observation of steel during creep-rupture at elevated temperature was photographed in 16mm cine film, by use of this apparatus.
    By analysis of the film, the structurad change during creep-rupture of steel were related with their creep curves. It was observed that the appearance of crack which led to the rupture occurred at the transition point between the secondary and the tertiary creep.
  • HOW TO DEAL WITH IRREVERSIBLE PHENOMENA

    pp. 1153-1158

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  • 熱経済技術部会報告(I)

    pp. 1159-1166

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  • 抄録

    pp. 1167-1173

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  • 鉄鋼ニューズ

    pp. 1174-1174

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  • 国内国外刊行誌参考記事目次

    pp. 1175-1179

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