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

Tetsu-to-Hagané Vol. 73 (1987), No. 1

  • Recent Development in Fractography

    pp. 19-25

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  • A New Departure of Long Term Creep Curve Prediction up to the Tertiary Stage

    pp. 26-33

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  • Current Trends of the Hydrogenation Reactor Materials for High Temperature and Pressure Services

    pp. 34-40

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  • Analysis of Impurities in Metals by Particle Accelerators

    pp. 41-54

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  • Preparation of Magnetic Fluid and Its Application

    pp. 55-63

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  • Report of the Activity of Joint Research Committee on Theory of Models and Scale-up Method/Isolation and Determination of Sulphides in Steel

    pp. 64-83

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  • The New Instrumentation System of Chiba Sinterplant and Its Effect in Kawasaki Steel Corporation

    pp. 84-90

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    An integrated systematization has been advanced as one of the means to cope with the recent development in ironmaking technology and energy demend/supply situations. This has been made possible because the processing capacity and safety in operation have been improved due to the advancement of the computer technology; the conventional analog control has been replaced by the overall digital control and just a single large-sized computer now allows the control of process computers which used to be installed independently in each factory.
    In the systematization, the construction work is proceeding with a view to reaching such a final goal as the realization of the unified control of the whole process in ironmaking works by means of a large-sized computer. As the first step, the construction of a new instrumentation system for a sintering factory has been made. This paper describes its function and effect.
  • Development of a Mathematical Model to Estimate Burden Distribution in Bell-less Type Charging for Blast Furnace

    pp. 91-98

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    Many types of burden distributions can be produced by bell-less type charging equipment tor BF. However, the change in configuration of burden layer occurs in a furnace top. Therefore, the accumulated state of burden has been investigated by using an experimental apparatus built on a scale of one third of Muroran No. 1 blast furnace, and a mathematical model to estimate the burden distribution has been developed.
    1) Materials charged at each turn of rotating chute form the burden layer with convex surface on the landing area.
    2) Ore layer formed after each turn of rotating chute shows different configuration before and after occurrence of the coke layer collapse.
    3) Change in particle size distribution depends on the charging conditions and gas flow. A regression equation expressing these relations has been obtained.
    4) On the basis of the findings, a mathematical model in which the in-furnace parameters affecting burden distribution are taken into consideration has been developed. This model has a feature in regard to introduction of the idea that the imaginary unit volume is given by dividing one dump volume of materials into many pieces and burden distribution is constructed by accumulation of the unit volume.
    By applying the mathematical model to Muroran No. 1 blast furnace, the suitable furnace operation has been obtained.
  • Peritectic Reaction andδ-γTransformation Mechanism in Carbon Steels

    pp. 99-106

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    Fe-C binary alloys and commercial carbon steel were quenched at various temperatures above and below the peritectic temperature. Petitectic reaction and the mechanism of subsequent transformation from δ phase to γ phase were investigated on the basis of solidification structure and measurement of carbon concentration by electron probe microanalysis in the quenched specimen. The result obtained are summarized as follows.
    When the peritectic reaction occurs, primary δ dendrites are isolated from surrounding liquid because γ phase is formed on the surface of the primary δ crystals.
    The γ phase nucleates successively in the untransformed primary δ crystals as temperature falls below the peritectic temperature and then conjugated concentration relationship between the δ and γ phases holds locally true. On the other hand, the γ phase formed on the surface grows into the surrounding residual liquid.
    As the γ phase elements nucleated in the untransformed δ region begin to interconnect with each other, the diffusion path for solute is progressively established, and carbon diffuses gradually through the γ phase formed on the surface to that nucleated in the untransformed δ region.
  • Effects of Nb and Ta on the Formation of "A" Segregation and Carbo-nitride in 12%Cr Steel

    pp. 107-114

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    Experiments are carried out on 12% Cr steel, which is widely used for such applications as generator components, to study the effect of Nb and Ta on the formation of "A" segregation and eutectic-type carbo-nitrides in the segregates.
    (1)Nb and Ta have an effect of making dendrite sturcture fine and reducing "A" segregation. Critical secondary arm spacing whether "A" segregation forms or not is around 600 μm.
    (2)In "A" segregation streaks, number of eutectic-type carbo-nitrides increases with increasing solute enrichment. The formation of the carbo-nitrides is promoted more strongly by the addition of Nb than that of Ta.
    (3)Carbo-nitrides form when the solidus temperature of "A"segregate is decreased down to the precipitation temperature of the carbo-nitrides which is around 1400°C.
  • Formation Mechanism and Prevention Method of Facial Cracks of Continuously Cast Steel Slabs Containing Boron

    pp. 115-122

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    Transverse facial cracks occurring in boron-containing CC slabs were fractographically analysed and the cause was found to be austenite grain boundary fracture due to the precipitation of BN along it. The embrittlement due to BN precipitation was very well simulated by the hot tensile test with Gleeble Tester.
    In order to avoid the facial cracks, two methods were proposed. One is the reduction of nitrogen content to satisfy the condition; (wt% Nt-0.2×wt%Ti)<0.003 wt%, and the other is the keeping of cooling rate less than 0.5°C/s in the secondary cooling zone to promote matrix precipitation of coarse BN.
  • Porosity Annihilation Process and Its Influences on Ductility of Rolled Steel Plates

    pp. 123-129

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    The effect of porosities on mechanical properties of plates rolled by heavy reduction and by light reduction per pass was investigated quantitavely in comparison with the effect of non-metallic inclusions.
    Compared with the strength and the toughness, the ductility such as the reduction of area in the tensile test and the upper shelf energy in the impact test is much more greatly affected by prosities than by elongated inclusions. It is possible to estimate the annihilating process of porosities from the viewpoint of the ductility as well as the ultrasonic examination.
  • Application of UV-curing Process to Steel Sheet with Lubricating Film

    pp. 130-136

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    In order to produce the steel sheet with lubricating film by UV (ultraviolet)-curing process, the composition of UV-paint; and the condition of UV-curing have been studied.
    The UV-paint is composed of an acryl-oligomer having carboxyl groups and one functional double-bond, monomer, photoinitiator and lubricant. The weight ratio of these components is 80:20:5:10. The acid value val of the UV-paint is 100. Line speed of sample for curing is 15 m min per an UV-lamp (O3 type, 80 W/cm). The steel sheet with lubricating film, whose thickness is 2.5±0.5 μm, is excellent in drawability, resisitibility against galling, alkali-removabilit and rust preventability.
  • Adhesion Durability in Composite-type Vibration-damping Steel Sheets

    pp. 137-143

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    In composite-type vibration-damping steel sheets, surface pre-treatment for the skin steel sheets has been examined and discussed for cold-rolled steel sheets, chromate-treated steel sheets, and electro-galvanized steel sheets (EG). The evaluation was based on the bond interface durability produced during salt spray testing up to 1000 h. Chromate treatment was confirmed to be the best surface pre-treatment for skin sheets, because it improves the primary (pre salt-spray-test) adhesion strength and prevents decreased secondary (post salt-spray) adhesion strength. EG has no ability to suppress the decrement of secondary adhesion strength, because Zn dissolves in water and edge-creep goes on. The failure mode in T-peel test changes from cohesive to inteface failure with decreasing secondary adhesion strength and with the occurrence of edge-creep.
  • The Effect of Transformation Latent Heat on the Progress of Phase Transformation during Continuous Cooling of Steel

    pp. 144-151

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    A study was undertaken to make clear the effect of latent heat evolution on the cooling transformation behaviour of steel. A method to estimate the influence of transformation latent heat on a cooling curve was developed on the basis of the cooling transformation kinetics. The present method was justified by comparing the cooling curve measured in steel SKS5 (an eutectoid steel containing Ni and Cr) with that estimated. The effect of latent heat evolution on the critical cooling rate was investigated. It was found that the effect of latent heat evolution was much larger on the lower critical cooling rate than on the upper critical cooling rate. Two types of continuous cooling transformation (CCT) diagrams were calculated; one with the cooling curves influenced by the latent heat evolution, and other with those controlled not to be influenced (i.e, controlled to be equal to those of transformation free). It was found that the C curves of the former CCT diagrams were located at higher temperature than the corresponding C curves of the latter, and this trend was stronger for the C curve of larger fraction transformed.
  • Calculation of Fe-C-S Ternary Phase Diagram

    pp. 152-159

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    The Fe-C-S ternary phase diagram was studied by computer calculation on the basis of the thermodynamic analysis of the Fe-S and Fe-C binary systems, together with the thermodynamic data on the Fe-C-S ternary melt. The Gibbs energy of individual phases was described by assuming both C and S to be interstitial atoms. The influence of ferromagnetism on the Gibbs energy of ferrite was also taken into account.
    The calculated results show that the remelting reaction occurs during the cooling process of Fe-C-S alloy. This fact was confirmed by scanning electron microscopy of the fractured surface of an Fe-0.93%C-0.02%S alloy. Furthermore, it was clarified that sulfur tends to reduce the single phase region of austenite significantly with its small addition, and the solidus temperature descends ata greater rate than the previous estimation made on the basis of experiment.
  • Temperature Rise and Deformation Behaviors of Materials during Fatigue Tests at Cryogenic Temperatures

    pp. 160-166

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    Measurements and discussions were made on the temperature rise of specimen during fatigue tests at 4K. In SUS310S stainless steels and tension-tension (R=0.01) tests, temperature rise was negligible under the stress of the proof stress even at 10 Hz. In tension-compression (R=-1) tests, however, a hundred times of the temperature rise occurred compared with those at R=0.01. In SUS304L steel, which has low proof stress but the work hardening accompanied by the stress-induced martensitic transformation occurs in low temperatures, the temperature rise was rather small compared with SUS310S steels. The difference in the magnitude of the temperature rise especially between at R=0.01 and at R=-1 depended on the magnitude of the plastic deformation. The upper limit of the fatigue frequency (temperature rise<1K) was, which also varied with the applied stress and materials, 5Hz at R=0.01 and 0.1 Hz at R=-1.
  • Effect of Mo Content and Heat Treatment Conditions on Hydrogen Attack of Steel for Pressure Vessel

    pp. 167-174

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    It has been shown in previous paper that good toughness of 1/2Mo steel could be obtained when the rate of cooling from the normalizing temperature was controlled to obtain a bainite content of 40% or more in the microstructure and tempering was conducted at a temperature about 650°C1). In this paper, metallurgical investigations were carried out relating to the deterioration in toughness caused by hydrogen attack and the effect of the above-stated toughness improving conditions on this resistance.
    Hydrogen attack is observed in 1/2Mo steels utilized in heat exchangers, pipes and their fittings which were operated in a hydrogen environment below the safety limit shown in the API Nelson chart revised in 1983. In recent years, therefore, the reexamination of the susceptibility to hydrogen attack of 1/2Mo steels has been a matter of concern.
    The effects of Mo content, microstructure and tempering temperature on hydrogen attack susceptibility of steel for pressure vessel were investigated by the specimens exposed to hydrogen at 450 and 500°C under 150kgf/cm2 G.
    From the test results, it was confirmed that the resistance to hydrogen attack was improved with increasing Mo contents. In terms of the relationship between the resistance to hydrogen attack and the toughness behavior of 1/2 Mo steel, it was also confirmed that the hydrogen attack deterirated the toughness, but the toughness-improving conditions of 1/2 Mo steel mentioned above reduced hydrogen attack susceptibility.
  • Effect of Postweld Heat Treatment on Critical Temperature in Hydrogen Attack of 1/2 Mo Steel Welds

    pp. 175-182

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    Relationship between a critical temperature in hydrogen attack and postweld heat treatment conditions was shown by a metallurgical investigation that was conducted to make clear a preventive measure of failures occurring in 1/2 Mo steel welds of heat exchangers and pipe lines which had been used in oil refineries and petrochemical plants.
    The authors examined degradation of tensile properties, susceptibility to intergranular cracking and bubble formation behavior in both actual welds and a simulated-heat-affected zone material (simulated HAZ) after a hydrogen exposure in the temperature range from 320 to 500°C under a pressure of 100 or 150 kgf cm2 (9.81 or 14.71 MPa).
    Postweld heat treatment at a temperature range from 550 to 650°C produced a significant improvement in hydrogen attack resistivity of the actual weld. In addition, an examination result of the simulated HAZ exhibited to produce a maximum critical temperature in hydrogen attack by excuting a heat treatment at around a temperature of 650°C. It was concluded that the highest resistivity to hydrogen attack was able to maintain provided a postweld heat treatment would be performed in the temperature range between 625 and 650°C.
  • Effect of Carbon on High Temperature Creep Property of a Ni-20Cr Alloy

    pp. 183-190

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    Changes in the creep resistance and dislocation substructure with addition of carbon have been studied in the temperature range between 900-1050°C, by using high purity Ni-20Cr alloys containing carbon up to 0.032wt%.The creep resistance of the alloy increased at the temperatures less than 1 000°C, with increasing of carbon content dissolved in γ-matrix. Such a strengthening effect was presumed to be caused by solid solution of carbon, and was associated with increase in dislocation density within subgrains. At 1050°C, the formation of subgrains or the dynamic recrystallization took place in the alloy with 0.032wt% carbon and these microstructural changes brought the decrease in the creep resistance of the alloy. The precipitation of carbide (M7C3) at the grain boundaries significantly increased the creep resistance, and this phenomenon was very similar to the grain boundary precipitation strengthening effect by α2-W phase in Ni-Cr-W alloys.
  • The Relationship between Internal Cracking and the Austenite Grain Boundary Segregation of Sulfur Atoms in 9% Ni Cast Steels

    pp. 191-198

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    The effect of austenite grain boundary segregation of S atoms on internal cracking in 9% Ni cast steels has been studied mainly by means of Ion Microprobe Mass Analyzer (IMMA).
    Internal cracks originate at the austenite grain boundaries which are also primary dendrite interfaces. Internal cracking, however, is not due to the formation of the grain boundary layers of low melting point substance, but arises from the decrease in grain boundary cohesion by S segregation. The segregation of S atoms is largely reduced by Mo addition and such an effect of Mo addition has also been discussed.
    x

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    1. The Effect of Transformation Latent Heat on the Progress of Phase Transformation during Continuous Cooling of Steel Tetsu-to-Hagané Vol.73(1987), No.1
  • Effect of Si on the Strength and the Toughness of Boron Treated Cr-Mo-Nb Steels

    pp. 199-206

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    Effect of Si content on the various mechanical properties and microstructures in B-treated Cr-Mo-Nb steels has been investigated.
    1) By increasing Si content, Charpy transition temperature of shear area (vTrsraises due to solution hardening and coarsening of austenite grain size, when coarse boro-carbides are not formed along grain boundaries during tempering treatment at high temperature.
    2) Si suppresses the coarsening of intergranular boro-carbides in case of high temperature tempering. As a result, in a steel containing excess dissolved B and so having boro-carbides along grain boundaries, it is considered that Si does not change vTrs spite of solution hardening and coarsening of austenite grain size due to increase of Si content.
    3) In an as quenched condition, austenite grain boundaries in a low Si content steel are clearly revealed, but those in a high Si content steel are not clearly observed after conventional etching. Consequently, it is considered that Si affects the grain boundary segregation.
    x

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    1. Effects of Mo Addition and Austenitizing Temperature on Hardenability of Low Alloy B-added Steels ISIJ International Vol.42(2002), No.10
  • Mechanical Properties of Cast Stainless Steels at Low Temperatures

    pp. 207-214

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    In order to estimate and predict the strength of cast or welded structural materials at 4K, the mechanical properties of columnar parts of cast austenitic stainless steels were investigated. Compared with hot-rolled materials, the mechanical properties of cast materials at 4 K were rcduced to 65-84% in tensile properties and 26-36% in absorbed energy. Fracture surface of tensile and impact specimens at 4 K showed the reained dendrite morphology and cracks were observed in matrix. The impact properties of cast materials at 4 K were improved by solution heat treatment. The mechanical properties of cast materials were affected by not only delta-ferrite content but also solidification structures
  • 鉄鋼の研究について考えること

    pp. 215-216

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  • 抄録

    pp. 222-223

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