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

Tetsu-to-Hagané Vol. 49 (1963), No. 13

  • 第66回講演大会について

    pp. 1859-1860

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  • The Travel of Raw Material and the Distribution of Temperature in the Rotary Kiln

    pp. 1861-1868

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    In the previous paper we described the installation of a multi-purpose 46 m long kiln with 6 sampling holes and the method of taking samples from a reducing kiln while it is in operation, then showed some results of measuring works.
    In this paper we discuss the travel of material and distribution of its temperature. Many literatures are found which investigate the transportation of raw materials, through a rotary kiln in the field of cement industry. From the viewpoint of roasting reaction, the material is composed of a single element for a cement kiln; however, it is always a mixture of 2 elements 'which consist of reducing agent and substrate for a reducing kiln. Then if segregation occurs between 2 elements, it means an interruption of reducing reaction in the kiln.
    So the segregation of material is one of the most important facts in the reducing kiln.
    After various experiments, researches and observations, we reach the following conclusions;
    (1) Segregation occurs because of different repose angles of material grain.
    (2) Travelling speed of grain through the rotary kiln is decided by the filling ratio of charge and its local position in the bed.
    (3) The grain of iron sand is so fine, and the reducing agent is not so fine, and as the result, the reducing agent has tendency to segregate outside of bed. We call it belt type segregation.
    (4) Belt type segregation grows into rippling distribution across the axis of kiln, we call it striped segregation.
    It is necessary for reductive roasting with kiln to control the grain size of charge material. In the future reports we shall analyse the segregation quantitatively again.
    Generally, a reductive kiln has three zones by the name of drying, heating and reducing zone. Measured distribution of material temperature is almost linear throughout its length, and the rate of heat transfer in the last zone by means of improvement on heat transmission and prevention of segregation in charge material.
  • Viscosity and Fluidity of High Alumina Slag

    pp. 1869-1873

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    It is expected in the near future that the ratio of the southern are in charge for B.F. will increase in Japan. Then, alumina contents in B.F. slag will amount to more than 20%.
    This paper deals with the fundamental study of viscosity and fluidity of high alumina slag at high temperature.
    The results of study are as follows.
    When alumina contents in B.F. slag increase, viscosity at each temperature increases.
    When basicity of high alumina B.F. slag increases, viscosity at high temperature (about 1550..) decreases, but viscosity at slagging temperature increases.
    Addition of MgO, Na20 to high alumina slag makes viscosity and fluidity decrease. When measuring fluidity at constant pouring temperature and constant mould temperature the measured results become highly reliable, and close mutual relations are found between fluidity and liquidus temperature (at this temperature viscosity reachs 20 poise), or between fluidy and viscosity at pouring temperature.
  • Measurement of Chemical Activities in Lead-Tin Binary Liquid Solution

    pp. 1873-1879

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    The activity of tin in lead-tin binary liquid solution has been measured by the oxygen concentration cell technique at 700.., 800.., and 900... The activity of tin deviates in a positive direction from ideality, with the deviation increasing with decreasing temperature.
    The activity of lead was obtained by the Gibbs-Duhem equation and it also shows the posi -tive deviation from ideality. The free energy of solution of the lead-tin system as well as the excess free energy of solution was calculated. Also, the partial molal free energies of lead and tin were calculated. The cell employed is as follows:
    Pb-Sn liquid alloy-SnO2|ZrO2-CaO|Sn-SnO2 (EMT=-RT/nF in asn)
  • On the Effects of Treating with Synthetic Powdered Slag on a Carbon Steel

    pp. 1879-1885

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    Molten carbon steels were treated with a small quantity of synthetic powdered slag consisting of CaO, Al2O3 and so on at pouring period in order to accelerate the desulfurization or deoxidation, and to change the shapes and qualities of inclusions and improve the steel qualities.
    It was found that (1) the desulfurization of molten steel advances rapidly and (2) mainly the sulfide inclusions decrease and the stringer-type inclusions do in the case-hardening steels and (3) larger inclusions turn into smaller inclusions and (4) the toughness of steels, particularly, its impact value, is improved remarkably.
    Thus, it was evidenced that the treatment of molten steel with synthetic powdered slag would be useful for the rapid refining of steels.
  • The Measurement of Modulus of Elasticity at High Temperature and Coefficient of Thermal Expansion for the Comparison of the Rate of Frequency of Thermal Stress Crackings in Various Steels

    pp. 1885-1891

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    According to the kinds of steels there are some differences in the frequency of thermal stress crackings which occur in the heating process of ingots. In this report, we measured Young's modulus and the coefficient of thermal expansion of typical steels, within the temperature range of room tempereature to 1000°C, because they influence the thermal stress. And using the results we compared the rate of frequency of thermal stress crackings according to the kinds of steels.
    The results obtained are as follows:
    (1) It was found that the Young's modulus decreases rectilinearly up to 400°C and curvilinearly over about 500°C to 600°C in all the steels tested. And the modulus is not influenced greatly by a small change of the components, the inclusions heat treatment, etc. of steels, but there is some difference among the kinds of steels classified roughly.
    (2) As for the coefficient of thermal expansion there is little difference with a small change in heat treatment for the same kind of steels but a considerably large difference according to the components of steels. This influence of the components is not very great under the transformation point but it becomes very great above the point (i. e. Austenite range). Especially when carbon content increases, the coefficient of thermal expansion increases heavily.
    (3) To estimate the magnitude of thermal stress which occurs when steels complete the transformation we utilized Young's modulus and coefficient of thermal expansion, and found that thermal stress increases chiefly in accordance with the increase of carbon content.
    It follows from this that thermal stress is greatest in hyper-eutectoid steel of JIS SK2, SUJ 2, 3. Consequently we can conclude that thermal stress crackings are most liable to occur in these kinds of high-carbon steel.
  • On the Relation Between Austenitic Grain Size and Creep Rupture Strength of Steam Turbine Shaft Forgings

    pp. 1892-1899

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    To make clear the cause for the dispersion of the creep rupture strength of large sized steam turbine forgings made of a Cr-Mo-V steel, the relations between austenitic grain size and creep rupture strength of the rotors were investigated. The creep rupture and tensile specimens were cut from the body ends of the rotors. Creep rupture tests were carried out at 510°C, 538°C, 565°C and 593°C, excepting those of rotor H which were carried out at 565°C. The austenitic grain was revealed by J. B. Cohens' etchant. On the other hand, to make sure of the test results on actual rotor forgings, the creep rupture strengths of specimens austenitized at various temperatures were investigated. The results were as follows.
    1. It was found that a relatively large difference of the actual a astenitic grain size existed between those of rotors, and the creep rupture strength of the rotors increased with an increasing mean actual austenitic grain diameter.
    2. And it was ascertained by the test results on the tendency to grain growth of the rotors that the rate of grain growth is comparatively fast at about 960°C which is the austenitizing temperature of actual rotor forgings.
    3. Creep rupture test results of specimens austenitized at laboratory also indicated that the creep rupture strength of the specimens was markedly affected by only the differences of austenitic grain size.
    4. According to the results mentioned above, it may be concluded that the dispersion of the creep rupture strength of steam turbine rotor forgings largely stems from the differences of actual austenitic grain size which are due to the change of the austenitizing temperature of the rotors.
  • Effect of Quenching and Tempering Temperature on High Temperature Properties of 1Cr-11 / 4Mo-1/ 4V Steel

    pp. 1899-1906

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    1Cr-11/4 Mo-1/4V steel has been widely used as steam turbine rotor shaft material. It is susceptible to notch brittlness during creep unless it is properly heat treated. The present study was carried out to make clear the effect of quenching and tempering temperature on the creep rupture (smooth and notched) properties of 1Cr-11/4Mo-1/4V steel.
    No. 1 specimen was quenched with 70°C/mn from various temperatures between 900 and 1050°C and tempered at 660°C for 68 h. No. 2 specimen was quenched with 70°C/mn from 955°C and tempered at various temperatures between 600 and 700°C. The obtained results are, summarized as follows.
    Low-temperature quenched material had very fine grains, low smooth rupture strength, high ductility and was not susceptible to notch. However, with an increase of quenching temperature it showed coarser grains and higher tensile and creep rupture strengths, but lower rupture elongation, lower ductility and higher notch sensitivity during creep. Impact properties were very susceptible to quenching temperature. With an increase of tempering temperature the material showed lower tensile strength, higher ductility and lower notch sensitivity. Notch sensitivity was associated with either high quenching temperature or low tempering temperature.
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    Readers Who Read This Article Also Read

    1. Study on Low-Chromium Heat Resisting Steels for Inlet Values Tetsu-to-Hagané Vol.50(1964), No.1
    2. 特許記事 Tetsu-to-Hagané Vol.49(1963), No.11
    3. 共同研究会製銑部会報告書 Tetsu-to-Hagané Vol.49(1963), No.9
  • Study on 20Cr-11Ni-2Mo-0.2P type Heat-resisting Steel

    pp. 1906-1914

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    Some austenitic heat resisting steels containing 0.2% phosphorus for exhaust valves have been evaluated by stress-rupture test at 650, 750 and 800°C, short time tensile test at room and high temperature, hot hardness test, lead oxide crucible test and scaling test. The addition of 0.2% phosphorus increases the precipitation hardening effect produced by carbide precipitation and results in marked improvement of rupture strength. The steel containing 0.3% C, 20% Cr, 11% Ni, 2% Mo, 0.2% P and 0.01% B has a good combination of strength and ductility, and is found suitable for heavy duty exhaust valves.
  • The Phase Diagram of The Fe-Cr-N System

    pp. 1915-1921

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    The tentative phase diagram of an Fe-Cr-N system in the composition range of 12 to 60% Cr, N up to about 2% at the partial pressure of nitrogen in air has been constructed by thermal analyses of Fe-Cr-N alloys which contained less nitrogen in the previously reported experimental formula [Cr] =32.9 log [N] +4.1.5, and X-ray analyses as well as microscopic examinations. Besides molten alloys, Fe-Cr-N alloys were prepared by the nitrogen-absorption at 1250°C and at one atmospheric preesure of pure nitrogen, and their structures have been examined. The denitrogenization of the nitrogen-absorbed alloys during the heating in the vacuum has also been clarified. The results are summarized as follows.
    (1) It was presumed from the study of the heterogeneous equilibrium of the Fe-Cr-N system that a peritectic reaction L+δ γ exists in the Fe-rich melt of the Fe-N system as seen in that of the Fe-C system, and it was also assumed that a eutectic reaction L δ+Cr2N exists in the range up to 11.6%N at Cr2N in the Cr-N system.
    (2) The peritectic reaction at the Fe-N alloy-side lowers the temperatures as the Cr content in the melt increases, and the eutectic reaction at the Cr-Cr2N alloy-side also decreases the temperatures as the Fe content in the melt increases. The above two mono-variant reactions meet at the point s in Fig. 1, which is found to exist at 16%Cr and 0. E9%N and at 1328.., and a peritecto-eutectic reaction L+δ γ+Cr2N is formed, the composition range of the non-variant reaction being in the hatched area formed by the following four points: q (δ), u (γ), s (L) and Cr2N.
    (3) It is presumed from x-ray diffraction analyses of alloys quenched immediately after their solidification that Cr2N does not dissolve Fe, Cr or N; the nitride primarily separated from melts may be shown as the simple form of Cr2N.
    (4) When Fe-Cr alloy sheets are heated at 1250°C at one atmospheric pressure of nitrogen, the higher the chromium content of the alloys, the more the nitrogen-absorption and the shorter the time for the saturation of the absorbed nitrogen.
    (5) When Fe-Cr alloys in the composition range of 12 to 40%Cr are nitrogen-absorbed at 1250°C, austenite is formed irrespective of the concentration of chromium in the alloys, and the phase containing chromium up to 23% decomposes into martensite on quenching and decomposes into α + Cr2N on slow cooling to room temperature, while the austenite containing above 23% Cr is retained as austenite without being decomposed by water-quenching from high temperatures.
    (6) Nitrogen-absorbed Fe-Cr-N alloys are denitrogenized by heating in the vacuum, the degree being less in higher chromium alloys.
  • Activity af Carbon and Oxygen in Liquid Iron

    pp. 1922-1930

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  • On Trend of the Analysis of Iron and Steel

    pp. 1931-1946

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  • 抄録

    pp. 1947-1950

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  • 特許記事

    pp. 1953-1957

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  • 日本学術振興会記事

    pp. 1958-1961

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  • 第66回講演大会見学会見学記

    pp. 1962-1967

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  • 鉄鋼ニューズ

    pp. 1968-1969

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    x

    Readers Who Read This Article Also Read

    1. Study on Low-Chromium Heat Resisting Steels for Inlet Values Tetsu-to-Hagané Vol.50(1964), No.1
    2. 特許記事 Tetsu-to-Hagané Vol.49(1963), No.11
    3. 共同研究会製銑部会報告書 Tetsu-to-Hagané Vol.49(1963), No.9

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