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

Tetsu-to-Hagané Vol. 66 (1980), No. 2

  • Density and Surface Tension of CaF2-based Binary Melts

    pp. 169-178

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    Densities and surface tensions of CaF2-(MgF2, BaF2, SrF2, NaF, LiF, CaO) binary melts were measured by the Archimedean method and the maximum bubble pressure method, respectively. The results obtained were summarized as follows:
    (1) The molar volumes of binary melts were calculated from their densities at 1550°C. For all of measured systems except molten CaF2-MgF2 system, volume changes of mixing were not observed, while for molten CaF2-MgF2 system negative volume change was observed slightly.
    (2) The surface tensions of molten CaF2-SrF2 system at 1 550°C were explained on the basis of the equation for the surface tension of ideal solution proposed by Guggenheim, while those of the other systems were explained on the basis of the equation for the surface tension of regular solution proposed by Guggenheim.
    (3) From the relation between surface tension and molar volume of CaF2-based binary melts, it was supposed that the surface tensions of those melts were dependent on the packing of fluorine ions on surface layer of melts.
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  • The Effect of Selenium and Tellurium on the Surface Tension of Molten Iron and Wettability of Solid Oxide

    pp. 179-185

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    Effect of alloying elements (oxygen, sulfur, selenium and tellurium) on the surface tension of molten iron and contact angle of molten iron on solid oxide (sintered alumina) were investigated with sessile drop method at 1 600°C. The surface tension of molten iron decreased with addition of these elements and tellurium was highest surface active element in this work (Te>Se>S>O). The contact angle of molten iron on alumina decreased with increasing of oxygen content in molten iron but increased with increasing of selenium or tellurium content in molten iron. The sulfur content did not have effect on the contact angle. The work of adhesion and interfacial energy between molten iron and alumina were calculated by using the experimental values of surface tension and contact angle.
  • Interdiffusion in Molten Fe-C Alloy

    pp. 186-193

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    The isothermal interdiffusivity was studied for molten binary Fe-C and quasi-binary Fe-C-Si alloys at 1 550°C by the diffusion couple method. The experiment was carried out by using a narrow alumina tube as a diffusion chamber under refined argon atmosphere in an electrical resistance furnace. The results can be summarized as follows;
    Dc=(1+0.24[%C])×10-4 cm2/s(0.33%C)
    Ds/ci = 1.01.4×10-4 cm2/s(0.5%C, 01.34%Si)
    Dc/si =6.9×10-5 cm2/s(0.3%C, 0.4%Si)
    where Dj/i is the interdiffusion coefficient of i in the quasi-binary Fe-i-j alloy. Discussion was held on the experimental procedure as well as the results investigated. Good agreement is concluded between the present measurement and some reference results which have been measured by the different method and estimated by the other suitable way.
  • Interdiffusion in Molten Fe-C-Si and Fe-C-Mn Alloys

    pp. 194-200

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    Ternary isothermal diffusion was studied in molten Fe-C-Si and Fe-C-Mn alloy which are of practical importance in steelmaking process. Two kinds of experimentation were carried out at 1550°C by the diffusion couple method; the first one is based on Fujita's solution4)6), the second on Boltzmann-Matano's solution for ternary system7). The results are summarized as follows:
    1) By the method I in Fe-C-Si system (0.304.88%C, 00.77%Si)
    Dcc=2.4±0.27, Dcsi=-0.03±0.19, Dsic=0.3±0.13, Dsisi=1.5±0.23.
    (×10-4cm2/s)
    2) By the method II in Fe-C-Si system (0.480.63%C, 0.080.55%Si)
    Dcc=1.141.86, Dcsi=0.010.50, Dsic=-0.210.11, Dsisi=0.330.97.
    (×10-4cm2/s)
    3) By the method II in Fe-C-Mn system (2.963.22%C, 2.473.69%Mn) Dcc=1.032.58, DCMn=-1.970.55, DMnC=-0.810.15, DMnMn=0.511.93.
    (×10-4cm2/s)
    Discussion shows that, due to the experimental limitation, the values measured by the method I are larger than those obtained by the method II. The results also satisfy the general properties of diffusion path.
  • Effect of Hot Rolling Conditions on Annihilation of Porosities in Continuous Casting Slabs

    pp. 201-210

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    Effects of hot rolling parameters on the annihilation of porosities in continuous casting slabs or ingots were investigated using specimens which include artificial porosities (sphere and cube). It was revealed that, of hot rolling parameters, the reduction ratio and the rolling shape factor are essential factors for the annihilation, whereas the rolling temperature is less influential. The following formulae was derived to predict the rolling conditions required for the annihilation of porosities.
    d0Hk/H0-∑kj=1Hk/Hjω0(C0+C1mj+C2m2j)≤0, mj=2√R(Hj-1-Hj)/(Hj-1+Hj) (j= 1, 2, ......k)
    where d0, ω0 : initial porosity size of thickness and width respectively, j : index of rolling pass schedule, Hj : plate thickness after j-th rolling pass (H0 : initial thickness), R : radius of work rolls, c0, c1, c2 : constants.
  • Development of Hollow Ingot for Large Forging

    pp. 211-220

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    A new method to make hollow ingots was developed to produce cylindertype forgings economically. The key-point of this method is the structure of the core which, consisting mainly of outer and inner steel pipes and intermediate special refractory, can readily be constructed, set in the mold and pulled out from the ingot, and which enables to control the cooling from inner surface of the ingot, without such defects as inner-side cracks.
    Large hollow ingots up to 140 ton can be made by this method with less segregation than that of conventional ingots and with such small porosities that close and diminish at forging ratio of about 2. Thus, hollow ingots are utilized as materials for high grade forgings, as pressure vessels, resulting in effective saving of production cost.
    Compared with conventional ingots, hollow ingots have following characteristics of solidification;
    (1) Total solidification time is short (2) Minimum solidification rate is high (3) Final solidification is not so rapid (4) Solidification from inner surface is slow.
    Every feature in the internal quality of hollow ingot can be explained from these characteristics of so-lidification.
  • Factors Affecting Necking Elongation of Steel Sheets

    pp. 221-230

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    Necking behaviour in tensile tests has been investigated for typical steel sheets. Local elongation in spontaneously necked region depends mainly upon the strain diffusibility of materials. Using specimens having artificial necking, a fomula describing this strain diffusibility has experimentally been deduced in relation to temperature and strain rate dependences of flow stress, and stress ratio. Furthermore, the relationship between necking elongation and macro-factors affecting it is formulated as follows,
    δn∝ΔP/P+0.22r/r+1
    where, δn : necking elongation, P: maximum load, ΔP : increment of maximum load with the change in tension speed from 10 mm/min to 100 mm/min, r: Lankford value in tensile direction.
  • Effects of the Structures to Impact Properties for High Carbon Steel

    pp. 231-238

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    There is a large demand for high carbon steel as parts of equipments and for machine structural uses and it is generally used as tough structures by heat treatment.
    In some cases, however, it is used in as-rolled pearlite structure (for instance, rails for railroads).
    The author investigated the effects of structures to impact properties for high carbon steel, by changing the temperature of reheating from 600°C to 1 300°C for sorbite and pearlite prior structures.
    The results are as follows. Sorbite is much superipr to pearlite. Finer structure is better in case of the same structure after heat treatment is pearlite, sorbite is better for the structure before heat treatment. When the heating temperature is higher than 1 100°C, the impact properties becomes worse regardless of the prior microstructure.
  • Damascus Steel Rediscovered ?

    pp. 232-292

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  • Effects of Microstructure on the Fatigue Property of High Carbon Steel

    pp. 239-243

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    Welding is usually avoided to apply for high carbon steel, however, in some cases welding is inevitable.
    In the present paper, investigation has been made on the metallurgical effect of quenched and tempered high carbon steel on the fatigue property, by carrying out a heat treatment corresponding to the heat affected zone of welding.
    The following results are obtained
    (1) In a ferrite-pearlite structure, simulated heat affected and as-forged specimens have a low endurance ratio as in the past data. Normalized specimen has a ratio about 0.37 which is an ordinary value in high carbon steel.
    (2) In a sorbite structure, the fatigue strength is higher than that of a ferrite-pearlite structure and also shows a higher endurance ratio.
    (3) These results are explained by means of fatigue crack initiation behavior in high-cycle fatigue region which depends on macro-and micro-imhomogeneity of materials. Therefore, a sorbite structure has a constant endurance ratio because the fatigue strength is determined by the average strength of matrix. On the contrary, a ferrite-pearlite structure does not show the linear relationship between fatigue and tensile strength, because the fatigue crack initiation does not depend on the matrix strength but on the locally weakest position, i. e. ferrite phase.
  • Shape Change of Sulphide Inclusions during Hot Bar Forging and Cold Wire Drawing and Its Influence on Mechanical Properties of High Carbon Steels

    pp. 244-252

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    This paper describes the deformation behaviour of sulphide inclusions (MnS) during hot working (forging and rolling) to bar and during cold drawing using high carbon steels.
    During hot working to bar, MnS first elongates and then breaks into pieces and each MnS becomes smaller. On the other hand, sulphide inclusions in REM treated steel remain almost globular during hot working.
    On cold drawing, MnS also becomes smaller due to both deformation and fragmentation. In REM treated steel, however, a large inclusion breaks into clustered pieces while a small inclusion stays globular and causes a crack in the vicinity of the inclusion in the drawing direction.
    Mechanical properties of the forged bar are determined in both longitudinal and transvefse directions after being normalized at 780°C. Although the reduction of area of the transverse direction decreases with increasing S content, the effect of S content decreases with the increases of the hot forging ratio.
    Up to 70% drawing reduction, an increase of S content decreases the ductility in the transverse direction of cold drawn steel, but over 70% the effect of S content disappears because the ductility is very poor.
    It is found that there is a correlation between the fracture strain and the sulphide inclusion area fraction on the fracture surface of tensile test pieces. This relation is maintained regardless of the amount and the shape of the sulphide inclusion, or of the test direction.
    However, the fracture strain of cold drawn steel, of over 70% drawing reduction, is determined mainly by the fiber structure of the matrix, caused by the severe drawing, and the above relationship disappears.
  • Improvement in Impact Properties of 80kg/mm2 Grade High Tensile Strength Steel Plate

    pp. 253-262

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    High tensile strength steel plate of 80kg/mm2 grade which contains rather higher Al content in order to make a small amount of boron effective, shows in some cases very poor impact property in transverse direction.
    Authors made systematic investigations about manufacturing processes from slab rolling to plate rolling as well as chemical compositions such as nitrogen and titanium.
    It was found that poor impact energy in transverse direction was caused by AIN which precipitated concentratedly at the austenite grain boundaries during slow cooling after slab rolling and afterwards on the stage of plate rolling modified its distribution to line in row to longitudinal direction.
    The ways to get the improved impact energy in transverse direction were also found as follows:
    1. lowering the finishing temperature in slab rolling below 1 100°C.
    2. increasing the cooling rate after slab rolling above 15°C/ min.
    3. raising the heating temperature before plate rolling above 1 100°C so that AIN re-dissolves.
    4. decreasing the nitrogen content as low as possible.
    5. a small amount of Ti addition.
    The methods 1-3 are intended to modify the distribution of AN and the ones 4-5 to decrease the amount of it.
  • Development of the Cr6+ and Cr3+ Continuous Analyzer for the Process Control of the Chromate Treating Solution

    pp. 263-270

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    The concentration of Cr6+ and Cr3+ in the chromate treating solution must be maintained exactly at the constant levels for getting the good coating.
    We studied in detail about the absorption curves of Cr6+ and Cr3+to develop the most suitable analyzer of Cr6+ and Cr3+ for the process control in the chromate treating plants. It was found out at the result of this study that the best method was to measure the absorbance at around 545nm and 620nm with the two wavelength spectrophotometer to determine Cr6+ and Cr3+. This colorimeter could be manufactured easily by the simple combination of the I.C. units.
    020 000ppm of Cr6+ and 02 000 ppm of Cr3+ in the chromate treating solution could be determined continuously by using this analyzer with the standard deviation (σd) of 105ppm (Cr6+) and 15 ppm (Cr3+) to the values of the chemical analyses. The stability of this analyzer in the running test of 12 hours was 110ppm (Cr6+ : 5 500ppm) and 17ppm (Cr3+ : 750ppm) in R (the difference between max. and min.).
    This analyzer was freed from the interference with Fe3+, Zn2+, So2-4, No3-, CH3COO-, suspended sludge, and bubble in the case of Cr6+ and Fe3+, Zn2+, So2-4, No3-, and CH3COO- in the case of Cr3+.
  • The Present Situation and Recent Development of Chemical Analysis Technology in Iron Works

    pp. 271-281

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  • 抄録

    pp. 297-304

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