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

Tetsu-to-Hagané Vol. 66 (1980), No. 10

  • Oxidation of Sulfur in B. F. Slags to Sulfate

    pp. 1459-1467

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    In order to remove the deteriorating effects of B. F. slag caused by the presence of sulfide, an investigation has been made of the oxidation of sulfide in B. F. slags to sulfate for samples in the form of planes or fluidized powders at 870 to 1200 °C.
    The results obtained are as follows:
    1) The optimum temperature to oxidize the sulfide to sulfate with suppressing the evolution of SO2 is 1100 to 1200 °C for slag planes, and is 900 °C for slag powders, the difference between the two being due to the sintering during the oxidation for the latter.
    2) The rate of oxidation of sulfide to sulfate is controlled by the diffusion of oxygen in the slag.
    3) The dissolution of S= into water from treated B. F. slags can be prevented when more than 90% of sulfur exists as sulfate.
    4) To achieve the result indicated in 3), it is estimated that slag powders of-200 mesh should be treated in the air for 2 hours at 870 °C, for example.
  • Removal of Tellurium out of Molten Iron

    pp. 1468-1473

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    The co-existence of a small amount of tellurium seems to improve deoxidation of steel with aluminum.The practical realization requires a subsequent treatment upon which the residual tellurium must be removed out of steel. The three experimental examinations led to the following conclusions:
    1) Ar stream can fast rid molten iron of tellurium. 40%-50% of tellurium was taken away for 20 min. under the present experimental conditions. The rate satisfies the general kinetic equation for vaporization of alloying elements.
    2) Rare earth metal is the most suitable substance to be added for the present aim, i. e. the removal of tellurium at low oxygen potential.
    3) A flux of CaF2-CaCN2 mixture is applicable instead of expensive REM. The mixture with a composition ratio of 1:1 succeeded in reducing the residual concentration of tellurium to about 20 ppm (rd. 90% reduction of tellurium) during 20 min. treatment with little change in the concentrations of oxygen, carbon and nitrogen in the melt.
  • Equilibria between Mn Alloy Melts Satulated with C and Various Kinds of Molten Slags and Calculation of the Activities

    pp. 1474-1483

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    In order to make clear the physical chemistry of the distribution reaction of Mn and Si between alloy melts and molten slags in the production furnace of high carbon ferromanganese and silicomanganese, the Mn-Si-Csat. and Mn-Fe-Si-Csat. alloy melts were equilibrated with MnO-SiO2, CaO-MnO-SiO2, CaO-MnO-Al2O3-SiO2 and CaO-MnO-Al2O3-MgO-SiO2 slags. From these experimental results, following thermochemical values were calculated by using the activities obtained previously by the author and some investigators;
    (1) The activities of Si in Mn-Si-Csat. melts at 1500 and 1550°C, and in Mn-Fe-Si-Csat. melts at 1500°C.
    (2) The activities of SiO2 in CaO-MnO-SiO2 molten slags at 1500°C.
    (3) The values of aMnO2/aSiO2 in CaO-MnO-Al2O3-SiO2 molten slags at 1500°C.
    (4) The values of aMnO2/aSiO2 in CaO-MnO-Al2O3-MgO-SiO2 molten slags equilibrated with Mn-Fe-Si-Csat. alloy melts at 1600°C.
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    1. Manganese Ores used for Production of High Carbon Ferromanganese Tetsu-to-Hagané Vol.49(1963), No.7
    2. Oxidation-Reduction Equilibria of Manganese in MntO-CaO-SiO2-Al2O3 Melts Tetsu-to-Hagané Vol.73(1987), No.16
    3. 雑録 Tetsu-to-Hagané Vol.41(1955), No.4
  • Thermodynamics of FetO-MxOy (MxOy= CaO, SiO2, TiO2, and Al2O3) Binary Melts in equilibrium with Solid Iron

    pp. 1484-1493

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    As a fundamental study of physical chemistry of steelmaking slags, equilibria between hydrogen-water gas mixture and liquid slags contained in solid iron crucibles have been measured for four binary slags of FetO-CaO, FetO-SiO2, FetO-TiO2 and FetO-Al2O3 systems at 1400 °C. From the data, the activity of iron oxide and the ratio of ferrous and ferric iron (Λ = Fe3+/Fe2+) were calculated for the composition of slags. In view of ionic theory, a regular solution model for cations was applied to evaluate the thermodynamic properties of complex slags from those of the binary slags. Three binary slags of FetO-SiO2, FetO-CaO and FetO-TiO2 systems conformed to the regular solution model within the experimental error except for the extremely FeO rich region. It was confirmed that the oxygen distribution between slag and metal was quantitatively expressed with this model over the wide range of slag composition.
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  • Rate of Hydrogen Desorption from Liquid Iron Alloys

    pp. 1494-1501

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    The rates of hydrogen desorption from liquid iron and several liquid binary iron alloys were measured by the carrier gas method using argon. The results obtained are summarized as follows.
    1. The rate of hydrogen desorption from liquid iron is governed by a first order reaction for hydrogen content in iron.
    2. The rate of reaction is largely affected by the agitation of liquid iron.
    3. The activation energy of the reaction obtained is a fairly low value of 5.7 kcal/mol.
    4. From the facts mentioned above, the rate of hydrogen desorption from liquid iron is controlled by the transport of hydrogen atoms in the boundary layer of the liquid phase, and the value of mass transfer coefficient in the inductively stirred melt is 3.16 × 10-2 cm/sec for pure iron at 1600 °C.
    5. As the effect of alloying elements, the reaction rate decreases with carbon and chromium contents, and increases with silicon content. Nickel has no measurable effect.
    6. A good correlation was found between the present values of mass transfer coefficients of hydrogen in the alloy systems and the diffusion coefficients of hydrogen in iron alloys reported by H. Bester and K. W. Lange.
  • Model Experiment and Theoretical Analysis on Structure of Inverse V-segregation

    pp. 1502-1511

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    Concerning the formation of macrosegregation in ingots, it is well known that the channels are smooth on the side facing outside of ingot and rough facing inside of ingot.
    In this work, these phenomena were reproduced by a model experiment of NH4Cl-H2O system and the progress of channel formation was precisely visualized. The experiment indicated that the channels were melted on the side facing outside of ingot and solidified on the other side, and that the interdendritic liquid flowed into the channels through the wall facing inside of ingot and a part of the liquid flowed out the channels through the other wall. The difference in the roughness between the both walls is theoretically explained on the basis of transport phenomena in this paper.
  • Study on the Descaling of the Steel Slabs before Hot Rolling

    pp. 1512-1521

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    The factors affecting on the descaling property of reheated steel slabs have been studied in the plate rolling shop. The frequency of scale defects is closely related to the amount of residual scale on the steel slabs after descaling by the hydraulic scale breaker. It is found in the rolling shop that the amount of the residual scale depends remarkably on the following two factors.
    (1) Degree of overheating in the furnace
    (2) Surface temperature of the scale on slabs immediately before descaling.
    On the other hand, it has been pointed out by many workers that the descaling property of Si-killed steels are worse than semi-killed steels. It is well known that fayalite is formed in the scale of Si-killed steel. In this study the effect of surface temperature of scale on the descaling property is mainly examined. It is found experimentally that the existence of fayalite causes the cracks in the scale during cooling.
    It could be concluded that the descaling property tends to be bad for the Si-killed steels when the cracks are formed in the scale before descaling.
  • Effect of Intercritical Rolling by Hot Strip Mill on the Strength and Notch Toughness of Plain Carbon Steel

    pp. 1522-1531

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    The application of the intercritical rolling on plain carbon steel, of which beneficial effect on strength and notch toughness was proved by laboratory mill experiment, has been made to hot strip mill.
    The following results are obtained:
    (1) Both spiral-welded and electric-resistance-welded pipes manufactured of intercritically-rolled coils show strength of X 52 grade and good notch toughness at low temperature.
    (2) Improvement of strength and notch toughness in intercritically-rolled coils are due to grain refinement of ferrite and pearlite which are transformed from worked austenite, and formation of substructure in ferrite worked in intercritical range.
    (3) No disadvantageous influence of intercritical rolling is observed such as lowering of strength or deterioration of notch toughness in welds in comparison to conventionally-rolled steel.
    (4) Though the intercritically-rolled coils have the texture in midthickness similar with that of cold rolled plate with strong fiber structure having<110>-axis parallel to rolling direction as main component, the mechanical properties as pipes are good as the change of properties due to pipe manufacturing is small and anisotropy of yield strength even decreases.
    It is concluded that the intercritically-rolled strip is suitable for structural steel required high yield strength and good notch toughness such as high-test line pipe.
    x

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  • A New Tempering Parameter and Its Application to the Integration of Tempering Effect of Continuous Heat Cycle

    pp. 1532-1541

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    A new tempering parameter (λ-value) has been defined basing on Arrhenius' equation so as to express the degree of tempering and to maintain the equivalence of time and temperature over a wide range of tempering conditions.
    Activation energy of the tempering process governing the changes in such mechanical properities as tensile and yield strength and hardness was determined by using a plain carbon steel and low alloy steels containing manganese, chromium and molybdenum. The activation energies obtained were to be 70 kcal/mol (295 kJ/mol) in carbon steel and about 100 kcal/mol (420 kJ/mol) in Cr-Mo steel, increasing with alloy contents.
    Using these activation energies, mechanical properties of tempered steel can be approximately expressed as a function of λ-value in a linear fashion for any combination of temperature and time, ranging from 400 °C to 700 °C and from 0.01 h to 1000 h, respectively.
    In addition, making use of the parameter, an analytical method of tempering effect is applied to a practical heat program by summarization of the tempering effects of two individual processes or integration of the tempering effect over a whole process of heat cylce in which temperature steadily changes. Predicted mechanical properties by this method were in good accordance with observed values.
  • Effect of Specimen Shape on the Delayed Failure Strength of High Strength Steel Prestressed by Partial Unloading

    pp. 1542-1549

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    The effects of two types of prestressing, i.e. partial unloading and perfect unloading, on the delayed failure strength have been investigated on various specimen configurations.
    The results obtained are summarized as follows:
    (1) Crack initiation time and 100 h delayed failure strength can be largely increased by two types o prestress methods, especially by partial unloading method, regardless of specimen thickness and notch root radius. The rate of increase of 100 h delayed failure strength by both prestress methods increases to converge to a certain value with increase of specimen thickness.
    (2) In order to raise the 100 h delayed failure strength by both prestressing methods, it is necessary to increase the unloading stress to a critical value, (σa)c, which increases with increase of specimen thickness and decrease of notch root radius.
  • Measurement of Apparent Viscosity of Ferrous and Non-ferrous Alloys in Liquid/solid Coexisting State-Fe-C, Sn-Pb, Al-Cu and Fe-Cr-Ni-C Alloys

    pp. 1550-1556

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    Measurement was made on viscosities of partially solidified binary alloys Fe-C (3 and 4%C), Sn-Pb (1.0, 1.5, 5, 15, 25, and 45%Pb), and Al-Cu (4.5 and 10%Cu), and iron-base alloys (Fe-2%Cr-1.5%C, Fe-25%Cr-20%Ni-0.4%C, and Fe-28%Cr-0.4%C). A rotating coaxial cylinder viscometer was used. Solid fraction was calculated for the observed temperatures with the aid of the equation proposed by Scheil. The viscosities were found to depend on the solid fraction, the cooling rate, and the shear rate, as has been reported by FLEMINGS.
    When the calculated value of solid fraction was more than 0.6 at the eutectic temperature, the relation between the viscosity and the solid fraction was similar to that for dispersed systems; that is, the viscosity increased remarkably in the range of solid fraction over about 0.5. When the calculated solid fraction at the eutectic temperature was less than 0.6, the viscosity rapidly increased after the temperature of alloy reached the eutectic one.
    The viscosity of the iron-base alloys was found to be affected more intensively by the cooling rate than by the shear rate.
  • Materials Problem in Coal Gasification and Liquefaction Processes

    pp. 1557-1564

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  • Recent Research Development of Amorphous Alloys in the U. S. A.

    pp. 1565-1568

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  • 良い英文を書くために/一カナダ人の見た1980年春季講演大会

    pp. 1569-1575

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  • 抄録

    pp. 1581-1587

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