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

Tetsu-to-Hagané Vol. 61 (1975), No. 10

  • 工業教育について考えること

    pp. 2319-2320

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  • The Equilibrium between Sulphur in Molten Iron and H2-H2S Gas Mixture

    pp. 2321-2327

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    To determine the thermodynamic properties of sulphur dissolved in liquid iron, the equilibrium in the reaction S+H2 (g)=H2S (g)
    was investigated for the temperature range of 1550-1700°C and sulphur concentration up to about 2 pct., using an induction furnace.
    Though these measurements have been done by many investigators, their results have scattered by such reasons as sulphur segregation in specimens and thermal diffusion of gas mixture.
    After the improvement for these many problems to be solved, the following equilibrium relation was obtained.
    log K (=pH2S/pH2·as) =-3200/T-0.863
    The activity coefficient of sulphur in molten iron, that is fs, decreased with the increase in sulphur concentration, however its decreasing rate became smaller with increasing temperature, indicating that iron-sulphur solution had a tendency to approach on ideal state with increasing temperature.
    The relationship among fs, sulphur concentration and temperature was given as follows, log fs=(-286/T+0.119)[%S].
  • Effects of Boron, Chromium, Molybdenum, Niobium, Tantalum, and Tungsten on the Activity Coefficient of Manganese in Liquid Iron Alloys

    pp. 2328-2336

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    The effect of alloying elements on the activity coefficient of manganese in liquid iron alloys has been measured using a closed chamber method with an alumina capsule. The results obtained are summarized as follows:
    (1) The results of interaction parameter eMn(X) in liquid iron alloys at 1570°C are given by
    (2) Enthalpy coefficient hMn(X) and entropy coefficient SMn(X) are obtained for X=B, Nb, and W as follows:
    (3) A linear relation with the correlation coefficient -0.83 is observed between εMn(X) and nX, eff..
    (4) The relations η Mn(X)=120εMn(X) and σMn(X)=63.1εMn(X) obtained in the present work yield the quantitatine relation between εMn(X) and temperature, the very low characteristic temperature of the solution, and the value TσMn(X)/ηMn(X) being close to unity. These relations and quantities are very different in magnitude from those of εN(X) or εH(X).
  • Effects of Rolling Condition on the Surface Temperature of Work Roll in Hot Strip Mill

    pp. 2337-2349

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    The roll surface deterioration is affected by the temperature of roll surface, and it shortens the roll life and decreases the availability of continuous mill products. This paper deals with the roll surface deterioration by analyzing effects of rolling condition on the surface temperature of work rolls in the finishing train of hot strip mill. A FORTRAN program for calculation of roll temperature with passschedule has been developed. The following were analytically determined by theoritical calculation.
    (1) Roll surface temperature becomes higher at the intermediate stands in a finishing train, but a heated surface layer is the deepest at roughing stands and it is shallower at finishing stands as rolling proceeds.
    (2) Roll surface temperature is more affected by rolled materials, and under the thinner gauge rolling it becomes higher, especially at roughing stands.
    (3) Surface temperature of work rolls which is continuously in contact with the strip is more affected by roll cooling at the outlet side.
    (4) Patterns of heat cracks on roll surface become finer at finishing stands than at roughing stands and they have been determined to be closely connected with heated surface layer of roll surface.
    (5) Damages on rolls such as big comet tail and scale banding in strip rolling are caused by severe heating, but it has been determined that such damage on rolls is possibly reduced by roll cooling.
  • Effect of Hot Band Heat Treatment on Planar Anisotropy of γ Value of Titanium Stabilized Steel

    pp. 2350-2362

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    Effects of heat treatments of hot rolled bands prior to cold rolling on the recrystallization texture and planar anisotropy of γ value have been investigated for 0.04°C-0.2°Ti steel sheets. The steels were hot rolled to the bands with slab heating temperature of 1000°C and 1250°C. The bands were heat treated at 600°C-1000°C for 1 hr, then 75% cold rolled and annealed.
    The heat treatments affected the preferred orientation of recrystallized texture and planar anisotropy of γ value, depending on the heating temperature of hot rolling. It seemed that the intensities of {110}‹001›, {100}‹01›, and {211}‹011› components of recrystallized steel sheets contributed to the planar anisotropy. Electron microscopic studies revealed that the size and distribution of TiC fine particles in the bands prior to cold rolling were markedly affected by the heat treatment as well as the heating temperature of hot rolling. It was suggested that these fine particles had an important effect on the development of the recrystallization texture.
  • Metallurgical Investigations on Continuous Annealing of Low-Carbon Capped-Steel Sheets

    pp. 2363-2374

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    Low-carbon capped-steel sheets having excellent drawability and ductility have been obtained by a continuous annealing process. Materials suitable for the purpose are low manganese steels (<0.25% Mn) with K values of 0-0.15, where the K value is defined as K=Mn(%)-55/16·O(%)-55/32·S(%)
    These steels are hot-coiled at high temperatures such as 670°C or above, and thencold-rolled. The time required for annealing at 700°C is about 1 min, which is extremely short compared with that required for the conventional batch annealing. As the optimum conditions for improving the ductility by controlling the distribution of carbides as well as the content of solute carbon, the cooling rate after continuous annealing and the subsequent over-aging temperature have been found to be 5-30°C/sec and 350°C-450°C, respectively. It should be noted that the ductility is much reduced when stresses exceeding some critical value (about 13kg/mm2 in the present case) are applied to the sheets during the over-aging treatment. Under the stress whose magnitude is not far less than the critical value, the over-aging treatment can be finished up in a short time. It is necessary, therefore, to install hearth rolls with large radii for the over-aging zone in a continuous furnace.
  • Effect of Discontinuous Change in Cooling Rate During Continuous Cooling on Pearlitic Transformation Behaviors of Steel

    pp. 2375-2390

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    In this investigation, the pearlitic transformation behaviour of steel with the cooling rate discontinuously altered during continious cooling was studied in relation to the CCT diagram of the steel. The main results are as follows:
    (1) The pea litic transformation behaviour with the cooling rate discontinuously altered during continuous cooling was diffe-ent from the transformation behaviour illustrated by usual CCT diagram.
    (2) The pearlitic transformation behaviour and the critical cooling rate with the cooling rate altered at a point during continuous cooling were observed to be related to the incubation period consumed before changing the cooling rate.
    (3) Including the degree of consumed incubation period in usual CCT diagram as a parameter, the transformation behaviour and the critical cooling rate can be estimated from a conventional CCT diagram.
    (4) If the same amount of the incubation period was consumed by either continuous cooling or isothermal holding, the transformation behaviour was virtually the same in subsequent cooling when the cooling started from the same temperature.
  • Effect of Aluminum Coating on Corrosion Resistance and Creep Rupture Properties of Heat Resisting Alloys in Fuel Oil Ash Corrosion Environment

    pp. 2391-2404

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    The protective effect on fuel oil ash corrosion of hot dipped aluminum coating was compared with that of calorizing for typical austenitic stainless steels by means of a furnace test method authorized by the Committee on Heat Resisting Metals and Alloys of JSPS in which specimens pre-coated with synthetic ash composed of 85%V2O5 plus 15%Na2SO4 were heated in air. The resistance to fuel oil ash corrosion for many kinds of typical heat resisting alloys before and a fte hot dipping was evaluated by the same test method. It was revealed that owing to higher aluminum concentration of surface layer hot dipping had very excellent protective effect on corrosion of these alloys.
    When the synthetic ash was pre-coated to specimens, remarkable decrease in creep rupture strength of SUS 316 steels resulting from an increase in minimum creep rate due to corrosion was observed. Hot dipping, however, raised the creep rupture strength of specimens pre-coated with ash to the same level as that of specimens without hot dipping and pre-coating of ash as a result of a decreas of creep rate due to prevention of corrosion. The effect of calorizing was less than that of hot dipping and the strength of steels was reduced in some degree in calorizing process followed by furnace cooling.
  • Alloy Design of Solid Solution Strengthened Nickel-Base Superalloy

    pp. 2405-2417

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    Alloy design is performed developing an intermediate heat exchanger alloy for atomic energy steelmaking, having good workability so as to be formed to tube and higher stress rupture strength than 1kg/mm2 at 1000°C-105 hours.
    171 compositions are extracted theoretically from about 17000 compositions in Ni-Co-Cr-Mo-W austenitic system and seven of them are examined experimentally. As a result, 16Cr-20W-30Co-Bal. Ni is established as one of the best austenitic compositions. Examining the effect of the addition of B, Zr, Y, and Al on the properties of 16Cr-20W-30Co-Bal. Ni and 20Cr-16W-30Co-Bal. Ni, Zr is proved to improve stress rupture strength and Al to promote internal oxidation in He.
    The finally developed alloy composed of (0.05C)-16Cr-20W-30Co-(0.5Ti)-0.05Zr-Bal. Ni seems to meet the target.
  • The Microstructure During High Temperature Aging of 25%Cr-28%Ni Austenitic Steels Containing Both Molybdenum and Nitrogen

    pp. 2418-2432

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    Two austenitic steels, designated as steel 22N (25%Cr-28%Ni-11%Mo-0.011%C-0.22%N) and steel 31N (25%Cr-28%Ni-2%MO-0.009%C-0.31%N), were used to study the microstructural changes during aging in the temperature range from 700° to 950°C for up to 5500 hr. Optical micrographs as well as back scattered electron micrographs were taken. X-ray diffraction phase identification was made in potentiostatically extracted residues. Lattice parameters of both austenitic matrix and precipitated nitrides were measured.
    In steel 22N, precipitated phases are mainly σ phase. No precipitation of Cr2N takes place above 700°C. In steel 31N, Cr2N and π phase (a nitride with the structure of β manganese type) precipitate on grain and twin boundaries. Volume fracion of π phase in the extracted residues increases with time of aging. Each precipitate can be identified either as π phase or as Cr2N in both back scattered electron micrographs and potentiostatically controlled etched optical micrographs. The chemical formula of π phase is derived from the composition of metallic elements to be (Cr, Mo)12 (Fe, Ni)8N4-y, where y represents a deviation of nitrogen concentration from the stoichiometric composition. The lattice parameters of both Cr2N and π phase decrease with time of aging. The lattice parameter of the austenitic matrix decreases also with time of aging. The lattice parameter decrease of steel 31N still continues at 800°C even after a few thousand hours aging. This implies that the precipitation of supersaturated nitrogen in this steel does not complete even after longer than 1000 hr.
    The high creep-rupture strength of this type of austenitic steels alloyed with nitrogen was chiefly ascribed to a so called solid solution strengthening on the basis of the above metallographic observations. The strengthening effect of Cr2N precipitation on grain boundaries was also discussed.
  • Effect of Molybdenum Addition on the Age-hardening Behaviours and Mechanical Properties of Fe-9%Ni-4.5%Mn Martensitic Alloy

    pp. 2433-2446

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    The age-hardening behaviours of an Fe-9%Ni-4.5%Mn martensitic alloy have been investigated metallographically concerning with hardness, strength and ductility. The effect of molybdenum addition on these properties of the Fe-9%Ni-4.5%Mn alloy has also been studied to obtain a good combination of strength and toughness. The results obtained in this paper are summarized as follows:
    (1) The age-hardening of the Fe-9%Ni-4.5%Mn martensitic alloy is due to the hardening by coherent strain associated with the two phase decomposition in martensitic matrix and the precipitation of NiMn. The 0.2% proof stress increases with increase of hardness but the embrittlement occurs simultaneously. This brittleness is improved with the precipitation of austenite in the overaging and softening stage. The addition of molybdenum to this alloy hardly changes its hardening behaviours whereas improves its ductility
    (2) In the Fe-9%Ni-4.5%Mn alloy containing 6%Mo, the similar age-hardening due to the precipitation of NiMn at 400-550°C with that in the Fe-Ni-Mn alloy is found and the age-hardening due to the precipitation of Fe2Mo is also observed at 500-700°C. The former hardening mechanism is Mott-Nabarro type and the latter one is Orowan type. These difference is clearly observed in the shape of stress-strain curves.
    (3) The optimum combination of strength and toughness is obtained in the Fe-9%Ni-4.5%Mn6%Mo alloy aged at 500°C for 10 hr having σ0.2=152kg/mm2, σB=162kg/mm2, δu=4.3%, δt=12.6% and φ=37%. The microstructure of this alloy corresponds to the aging stage in which Ni Mn particles are 150-200 Å in diameter, Fe2Mo particles are about 300 Å in diameter and austenite is not yet formed.
  • Study on Aging Processes of Maraging Steels by Internal Friction Measurement

    pp. 2447-2455

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    The maraging reactions of Fe-Ni-Cr ternary and Fe-Ni-Cr-Co quaternary alloys with and without Nb addition are studied by measuring internal friction and relative shear modulus during isothermal anneal in the temperature range between 300°C and 600°C for 5 to 10000 min.
    The results are summarized as follows.
    1) Several stages of internal friction and relative shear modulus changes are found and related to the following processes. I1; carbide precipitation, I2; short range ordering, I3, G1, and I4; precipitation and resolution of Nb containing metastable phase, G2; clustering of Cr atoms, I5 and G3; austenite formation, I6 and G4; recrystallization of formed austenite. The simple TTT diagrams which give the beginning and end of the aging reactions are proposed.
    2) Nb addition prevents the short range ordering in base alloys.
    3) Nb containing metastable phase precipitates at temperatures lower than 450°C and this phase resolves between 400°C and 500°C.
    4) The clustering of Cr atoms occurs in all samples, even in the alloy containing only 3.5%Cr.
  • Aging of 1% Cu-3% Ni-1% Al Steel

    pp. 2456-2466

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    Microscopic observations have been made on a 1% Cu-3% Ni-1% Al steel in the solution-treated and aged state in order to make clear the mechanism of aging induced by simultaneous addition of Cu, Ni, and Al.
    The extraction replica, transmission electon microscopic and electron diffraction studies have shown that precipitation of ε phase occurs in the initial stage of aging, and subsequently, B2 type super lattice intermetallic compound α′ phase (NiAl) precipitates preferentially at grain boundaries and with the progress of aging it precipitates in matrix. Identification and analysis of dispersed precipitates by EPMA have shown that Ni is enriched into dispersed precipitates with progress of aging.
    On the basis of these results, aging mechanism of the steel has been discussed.
  • Electron Diffraction on Strained Cementite in Steels

    pp. 2467-2477

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    In order to investigate the mutual relation between strained cementite and X-carbide, observations by transmission electron microscopy were made on internal defect structures and crystallographic natures of cementite in cold-rolled high carbon steels containing 0.86% and1.25% carbon. Thermomagnetic and X-ray diffraction measurements were also made for comparison's sake. The main results obtained are summarized as follows;
    1) The strained cementite in cold-rolled high carbon steels contains dislocation and the other defect structures of various types. The cementite which was suffered an extremely heavy straining has also fine strain markings and moire fringes of nearly 100Å in spacing.
    2) The electron diffraction pattern of strained cementite generally distorts as compared with that of cementite free from strain. The distorted electron diffraction pattern is, however, never agreeable with that of monoclinic X-carbide, showing that the strained cementite is not identified with X-carbide.
    3) Internal defect structures, the distortion of electron diffractin pattern, and the tangential spread ofdiffraction spot disappear by the annealing for 5 hr at 700°C.
    4) Raise in the curie point of cementite with the degree of cold-rolling is detected by the present thermomagnetic measurements. The result of X-ray diffraction of cementites in the cold-rolled steels shows peak shift, lowering of peak height, and broadening of diffraction line. Any peak from xcarbide is not detected. These results are consistent with the above electron microscopic observations.
    5) The strained cementite showing the distorted electron diffraction pattern is also observed in the tempered high carbon steels.
    From these experimental results, it is suggested that the strained cementite suffering some constraints from ferrite matrix in tempered steels is not regarded as X-carbide.
  • Analysis of the Noise and Improvement of the Flaw Detecting Ability on the Eddy Current Flaw Detector for Hot Wire Rod

    pp. 2478-2488

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    Recently, various eddy current flaw detectors have been used in the wire rod mill for the quality control, but, in general, these flaw detectors have been unable to detect the flaw below 0.15mm depth due to the various noises.
    In this paper, the analysis of the noise and the improvement of S/N by the phase discrimination are described.
    From the result of the frequency analysis of the noise, it was confirmed that the nois was generated mainly due to the vibration of the wire rod in the search coils and such a noise could not be fully decreased by the frequency filter or by the phase discrimination in the case of 40kHz carrier frequency.
    Accordingly, the new flaw detector with 160 kHz carrier frequency which enables decrease the noise by the phase discriminator was developed and could detect the small flaw as 0.1mm depth.
    This flaw detector has been installed and in operation satisfactorily at the Hoshizaki Plant.
  • On the Extraction of Large Inclusions in Steel by Slime Method and Classification According to the Size

    pp. 2489-2500

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    A study has been carried out to establish the rapid and reliable method of isolation of large inclusions (>50μ) in steels and classification according to the size.
    The results are as follows.
    1) A large quantity of slime obtained by electrolysis of steel are separated from inclusions about in an hour by ultrasonic sieving method (applied except Al killed steel) or by elutriation method using the improved apparatus.
    2) A small quantity of cementite and metallic iron particles are separated magnetically, and nonmagnetic iron rust is also separated similarly after the reduction to metallic iron. The quality of inclusions is not affected by this treatment. Inclusions attached to magnet with magnetic substance must be recovered by the Br2-CH3OH method or by picking up them observing through a microscope.
    3) Using the sieves, the obtained inclusions are classified reliably according to the size.
    4) The shape of silicate inclusions is hardly damaged by the ultrasonic vibration, but chemical treatment changes markedly their composition. On the other hand aluminate inclusions are chemically stable and very brittle.
  • Mechanical Properties of Metals and Alloys at Cryogenic Temperatures

    pp. 2501-2513

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  • 抄録

    pp. 2514-2519

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