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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 44 (1958), No. 10

  • ON THE WALL EROSION OF THE BLAST FURNACE

    pp. 1159-1164

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    Recently the life of a blast furnace has a tendency to be decided by the damage of wall bricks at the shaft. Higashida No. 5 blast furnace in Yawata Steel Works was one of these examples, too. This furnace had been operated for about seven years, and during the campaign the shaft-wall-brick had expanded and forced the charging assembly upwards about 1m. Consequently it was obliged to be blown out. In the dismantling work of the furnce the state of erosion and the changes of physical and chemical properties of bricks were investigated. And the structural changes of bricks were investigated with micro-photographs. The result of this investigation showed to a certatin extent the mechanism of brick degradation by alkalis, CO, Zn, Pb etc. in furnace gas penetrating through its pores, and the following counter-measures were devised.
    1. Use of bricks of compact structure.
    2. Shell-type construction with many cooling plates.
    3. Limitmg the use of raw material containing large amount of alkalis, Zn, Pb etc.
  • HEAT TRANSMISSION IN AN COIL ANNEALING FURNACE

    pp. 1165-1170

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    Difference between maximum and minimum temperature in steel coils, when heated for 25h. in an annealing furnace as shown in Fig. 1, is said to be 30-60°C. Theoretical calculation was carried out to know whether this temperature difference is inevitable or not, and reached the conclusion that this range can be reduced to about 5°C, or heating time necessary to get temperature difference within 30°C may be reduced to 15h.
    Discrepancy between theory and practice was caused by the following facts:
    1). Quantities of heating gas flowing into diffusors (B in Fig. 1) were not equal.
    2). Temperature of heating gas flowing into diffusors was high at upper diffusors, and low at lower ones.
    3). Outer parts of coils were heated by convection of gas and by radiation from heating zone (F in Fig. 1) whereas the tops and bottoms were heated only by convection. And as temperature of heating zone was higher than that of coil, temperature of the outer parts were apt to be high.
    As a heating source of furnace, radiant tubes were often used. Radiant tubes had some defects, i.e., initial cost was expensive, life was short, and thermal efficiency was low. The reason why these were used in spite of such defects, was perhaps due to the fact that distibution of temperature in heating zone was favourable. But, in a good design, uniformity of temperature in coils can be obtained in dependent of temperature distribution in heating zone. It was easy to design a furnace which gave the theoretical temperature distribution.
  • THE RELATION OF FORGEABILITY AND CAST STRUCTURES OF Timken 16-25-6

    pp. 1170-1175

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    There are many experiments on the forging of metals, but these are studied to know strain and stress at a impact working, or from the view point of strength of material. There are seldom from the view point of metallic material technology. For the present situation, the authors studied the forgeability of a less forgeable ingot from the view point of metallic material engineering.
    The samples used in this experiment are 15×15mm, and of columnar structure, granular one and both mixed. Forging temperatures are 800°C, 900°C, 1100°C and 1300°C. In the case of columnar stucture sample and both mixed one, they compressed impactly the columnar axis parralel to the forging directon (longitudinal) and these stand at right angle each other (transversal), and various phenomena were examined.
    Stress-strain curves are obtained by magnetic method. The results are as follows:
    (1) Working resistance decreases in the case of the compressive working of granular structure, transversal one and longitudinal one, one by one.
    (2) The difference of working resistance of (1) decreases with rising temperature.
    (3) When the working velocity increased, a tendeny to increase this difference were observed.
    (4) The relation between working degree log (h0/h) and working energy is linear in the range of this experiment. Here, h0: inital height of sample. h: height of sample after compression. (5) The crack forming possibility decreases with longitudinal columnar, granular one and tranversal one, according to the aforesaid order. (6) The forging temperature is a sensible factor of the crack forming possibility.
  • THE RELATION BETWEEN THE DEFECTS OF INGOTS AND THE SAND MARKS OF BEARING STEEL

    pp. 1175-1179

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    In the forth report, the authors studied the defects of the surface of ingot section, and examined whether these defects had connection with sand marks of the steel rod or not.
    The results are briefly summarized as follows:
    (1) Ingot defects are not changed by soaking, but analytical sands amount are changed.
    (2) Generally, the part of chill crystals and columnar crystals of ingots have few defects, but free crystals on outside have many large defects, and there are many small defects in inner free crystals. These defects are the non-metallic inclusions. There are many cavities in the center of the ingot, of which length is long and diameter is small.
    (3) The clearness of ingot is not always proportional to the number of sand marks of the steel rod.
    (4) There are some large non-metallic inclusions in the free crystal on outside of ingots and these defects are elongated in the course of rolling and grow up as sand marks of the steel rod.
  • FACTORS CONTROLLING THE GRAPHITIZATION OF HIGH CARBON STEEL AT SUBCRITICAL TEMPERATURE (Part-1)

    pp. 1180-1185

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    Several experiments has been made in an effort to reveal some of the factors controlling graphitization of pure high carbon steel deoxidized with aluminum and silicon. The results obtained were as follows:
    (1) Rate of dissociation of cementite was a maximum at about 650°C.
    (2) The reaction rate of dissociation of cementite was a maximum when the steel had been quenched previously in order to produce martensite, and less graphite formed in the furnace cooled, air cooled or isothermal transformed samples.
    (3) The heating at 1000°C for 2 hours and furnace cooling after water-quenching from 870°C inhibited very markedly the graphitization on subsequent anneal at 650°C. The treatment of heating above the critical apparently tend to destroy or render inoperative nucleation which would promote graphitization.
    (4) Cold drawing accelerated the formation of the graphite nuclei and the increase in the cold reduction to 50% produced a corresponding increase in the rate of graphitization.
    (5) The more graphite fromed in cold drawn samples of pearlitic structure than spheroidized state on subsequent annealing at 650°C.
  • BEHAVIOR OF THE CARBIDES AND HEAT-TREATMENT IN LOW-W AND LOW W-Co HIGH SPEED STEELS

    pp. 1186-1191

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    The report deals with a study on the behavior of carbides in low-W high-speed steel and low W-Co high speed steel.
    The total amounts of carbides in the several heat-treated specimens of the high speed steels were determined by electrolytic isolation method.
    Chemical compositions and crystalline structures of the isolated carbides were determined by chemical analysis and X-ray diffraction, and the shapes of the carbides were observed by electron microscope, and the following results were obtained.
    (1) In annealed states, the amounts of carbides in these steels are about 20-22% wt%, and about 85-95% of the W and V in the steels are concentrated in the carbides, while the most portions of the Si, Mn and Co are dissolved in the matrix. The carbides precipitated in these annealed steels are M6C, MC and M23C6.
    (2) In quenched states, the insoluble carbides in the high speed steels are only M6C, and it amounts to about 10 wt%, which is the same about 40% of the carbides in annealed state.
    (3) The more rises the tempering temperature, the more precipitate the carbides from the austenite. And, especially, the concentration percentage of the special alloy elements in the carbides increases suddenly at the tempering of 575°C, and MC carbide appeares in the steel by tempering at above 300°C.
  • EFFECT OF ZIRCONIUM ON THE AUSTENITIC GRAIN SIZE IN IRON AND STEEL

    pp. 1192-1197

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    The effect of zirconium on the austenitic grain-size refining and its grain-coarsening temperature in electrlytic iron and low-carbon rimmed steel nfelted in nitrogen atmosphere, in argon atmosphere and in vacuum were studied. The effect of nitrogen on the austenitic grain-size was also tested with electrolytic iron melted in nitrogen atmosphere, holding it for various time. When zirconium was added, the austenitic grain-size was refined and its graincoarseniding temperature became higher.
    In the case of electrolytic iron, grain size became finer in certratin range of zirconium content, but in mild steel such range could not be found. Total contents of oxygen or nitrogen did not effect directly on the grain size, but nitrogen coexisted with zirconium effected on grain size. Considering of grain-coarsening temperature, amount of inclusions which was to be cause of grain refining was calculated from thermodynamic data. It was considered that ZrN or ZrC were effective for grain refining but ZrO2 was not so. On mild steel, the authors could not obtain the obvious conclusion because of including several elements. It was presumed that the cause of grain size refining could be decided clearly if coexisted inclusions, ZrN, ZrO2, ZrC and etc., would be able to analyse separately.
  • DETERMINATION OF TOTAL Fe, TiO2 AND FeO

    pp. 1197-1203

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    This work was undertaken to find rapid chemical methods for the analysis of sand iron and ilmenite.
    The methods are shown in outline Fig. 1. As the chief source of error in ore analysis was found in the separations, and this takes most of the time, separations were avoided as far as possible. Most of the measurements were made photmetrically, and procedures were planned to involve a minimum of manipulation.
    Each constituent was determined independently, for example, in a first sample decomposed by fusion with Na2O2 in a nickel crucible and solution in H2SO4, after reduced with Znamalgam. Total Fe and TiO2 were determined by titration with KMnO4 using a NaWO4 indicator. SiO2, Al2O3, MnO, V2O5, Cr2O3, and P2O5 were determined photometrically. CaO and CaO plus MgO were determined by titration with EDTA. In a second sample decomposed by H2PO4 and NH4VO3, FeO was determined by titration with KMnO4. Accuracy was compared favorably with the former methods.
  • IRON SAND AND IRON SAND PIGS-A REVIEW-

    pp. 1204-1216

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  • A REVIEW OF STUDIES ON THE PERMANENT MAGNET

    pp. 1217-1224

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    The main subjects for research of permanent magnets were summarized in this lecture. High coercive force of new permanent magnets are to be expected when fine particle have either high crytsal anisotoropy or anisotoropy of particle shape. In this cases the particle consists of single magnetic domain, and any change of magnetization must occur by domain rotation.
    The magnetic energy products of permanent magnets are improved by manufacturing methods such as the formations of columnar grains, the treatements in a magnetic field or the cold working.
    Fundamental problem in efficient design of permanent magnets is to know the working of of permanent magnet in various applications. Leakage flux is comparable to effective flux.
    It should be determined the leakage factor to design quantatively.
    It is essential that the magnetic flux should be stable over long periods of time.
    External influences such as external magnetic fields, mechanical shock and magnetic shunt affect the magnetic flux of a permanent magnet. Spontaneous redistributions of domain magnetization may take place without any external influences.
  • アメリカにおける冶金学的研究の傾向

    pp. 1225-1233

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  • 抄録

    pp. 1234-1240

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  • 鉄鋼ニューズ

    pp. 1241-1241

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  • 国内国外刊行誌参考記事目次

    pp. 1242-1245

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  1. blast furnace
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  7. bubbling ladle
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