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

Tetsu-to-Hagané Vol. 57 (1971), No. 1

  • 新年を迎えての回顧と展望

    pp. 1-2

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  • 1970 Perspective of Production and Technique of Iron and Steel in Japan

    pp. 3-14

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  • Specific Surface Areas and Adsorption Volumes of Water Vapor of Ferric Oxides and Powdered Iron-Ores

    pp. 15-25

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    The specific surface areas of various ferric oxides and iron-ores were measured by BET method, using nitrogen and krypton as adsorption gas. The results show that those specific surface areas decrease remarkably with increase of heating temperature, however, they are little dependent on their particle sizes. They also depend on their kinds; for example, limonite has large values, 50-70 m2/g, hematite 2-40m2/g and magnetite 0.3-1m2/g.
    Furthermore, the adsorption volumes of water vapor on various iron-ores were determined. The adsorption of water vapour on those iron-ores may be regarded as physical adsorption and the adsorption volume of water vapor per unit surface area decreases with increase of specific surface areas.
  • On the Reactions between Non-metallic Inclusion and Matrix Metal in a Rimmed Steel

    pp. 26-36

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    Steel ingots are generally subjected to various heat treatments during processing to final products.
    For example, those are annealed for a long time in a soaking pit prior to rolling. In this period, there is a possibility that some reactions between non-metallic inclusions and matrix around them can occur.
    The reactions during annealing of ingot and slab of a rimmed steel were studied here by examining the changes in composition of inclusions and matrix by means of the electron probe microanalyser. Results obtained are as follows. 1) When the ingot was annealed at the soaking temperature for a long time, compositions of inclusions changed probably to attain the equilibrium with matrix at the temperature. The magnitude of such changes varied with the position in ingot, hence it was supposed to depend on the rates of solidification at each position. Some reactions may take place between inclusion and matrix and between components of inclusion such as oxide and sulfide. 2) In the case of slab under similar treatment, inclusions changed their shapes to spherical readily at above 1300°, and the compositions changed largely at 1100°C resulting in an increase of manganese concentration.
  • On the Heat-Treatment Characteristics of Chromium-Molybdenum and Nickel-Chromium-Molybdenum Carburizing Steels

    pp. 37-46

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    In order to establish an optimum heat-treatment condition of carburized parts to give an excellent combi-nation of high hardness and good toughness, the heat-treatment characteristics of some practical case-hardening steels have been studied by metallographic examination and hardness and static bending tests.
    The results are summarized as follows;
    (1) The transformation behavior of carburized layer and unaffected matrix of the steels SCM22, SNCM 21 and SNCM 23 during heating and cooling have been clarified with relation to the austenitizing temperatures, the conditions of heating to and cooling from that temperature and the carbon content.
    (2) In order to obtain high hardness of the surface of these steels quenched directly after carburization, the optimum surface carbon contents of the steels are 0.80 percent for SCM 22 and SNCM 21, and 0.70 percent for SNCM 23 series. In these case, however, 5 to 10 percent of retained austenite was observed.
    (3) The most important factor to obtain high hardness and toughness is the heating cycle after carburization, that is, the heating rate from A1transformation point to austenitizing temperature and the holding time at that temperature.
    (4) When SNCM 23, containing 0.80 percent carbon with bainitic or pearlitic structure is quenched in oil immediately after rapid reheating up to 850°C. Rockwell C scale hardness 66 to 67 were obtained.
    (5) It has been revealed by the static bending test that the absorbed energy of rapidly heated and quenched steels increases 30 to 60 percent compared with slowly heated ones.
  • On the Rolling Contact Fatigue Test of Back-Up Roll Materials

    pp. 47-58

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    In order to know the spalling phenomena and to develop the material for back-up rolls, the rolling contact fatigue strength of the back-up roll materials is examined by using 3 high roll type rolling contact testing machine. The problems tested here are the effect of microstructure, of forging ratio, of direction of flow caused by hot working and of the surface defects on the resistance to spalling. The results obtained are as follows:
    (1) The specimen with martensitic structure shows better rolling contact fatigue resistance than those with bainitic and pearlitic structures.
    (2) The materials with high yield strength is good for back-up roll materials from the point of resistance to spalling.
    (3) The effect of forging ratio on the resistance to spalling is very small; i. e. the resistance to spalling slightly deteriorates with increase of forging ratio, but this tendency is indistinct.
    (4) On the surface where metal flows cross to this surface, resistance to spalling is brought lower than else where.
    (5) Ghost spots behave as ductile part as same to matrix on the rolling contact surface.
    (6) Surface layer of rolling contact is work hardened. Within this layer, matrix flows plastically in the direction of rotating direction.
    (7) Initial crack of spalling generates on the surface and grows obliquely along the plastic flows and finally spalls by radial brittle fracture.
    (8) Defects caused by casting workmanship, if they are located within the surface layer flown plastically, will become the source of crack initiation during rolling contact.
    (9) The defects near the surface layer of the specimens make the resistance to spalling low, but it depends on the size and location of the defects.
    (10) It is very difficult to apply the results of rotating bending fatigue test to those of rolling contact fatigue test.
    From these results, it is suggested that the back-up rolls with high spalling resistance have martensitic microstructure, Vhigh yield strength and sound surface.
  • Effect of Small Additions of Ti and Nb on the Creep-Rupture Strength of High-Alloy Austenitic Stainless Steels

    pp. 59-67

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    Improvement of the creep-rupture strength of 18-8 stainless steel (Type 304) by additions of small amounts of Ti and Nb has previously been reported.
    Such effect of additions of Ti and Nb on the creep-rupture strength of high-alloy austenitic stainless steels such as 22Cr-12Ni or 25 Cr-20Ni has been studied.
    As a result, it was found that the combined additions of small amounts of Ti and Nb to high-alloy austenitic steels are also effective for improving the creep-rupture strength just like as the case of 18-8 austenitic steel.
    Further effects of additions of Ti and Nb were found to be as follows:(1) the shape and distribution of precipitated carbides change, (2) the carbide particles precipitate finely and are evenly dispersed. It is concluded that the improvement of creep-rupture strength is considered to be due to the improved dispersion effect of these fine carbide particles.
  • Fundamental Study on Isolation and Determination of Carbide in Steel

    pp. 68-85

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    Fundamental study on isolation and determination of various carbides in steels was carried out by means of hydrochloric acid, sulphuric acid, phosphoric acid, and potentiostatic electrolytic methods.
    The results are as follows:
    1. TiC, VC and NbC are very stable chemically, and are isolated by the electrolytic method quantitatively, and even by any mineral acid method easily.
    2. ZrC in steel in relatively unstable and is decomposed gradually with the mineral acids. It is, however, able to be isolated by the electrolytic methods using any electrolyte.
    3. Cr7C3/(Cr, Fe)7C3and Cr23C6/(Cr, Fe)23C3are isolated by the phosphoric acid method at room temperature. In case of isolating the chromium carbides, the electrolytic method is often adopted, but those using dilute hydrochloric acid and hydrochloric acid-ethyl alcohol or-ethylene glycol show more or less lower yield of the chromium carbides than former.
    4. Mo2C is so unstable chemically that it decomposes not only in some mineral acids but also in water and alcohol. It is, however, isolated by means of the acid method using phosphoric acid (2+1), and by means of the electrolytic method using sodium citrate almost quantitatively.
    5. Fe3C/(Fe, M)3C is isolated nearly quantitatively by the electrolytic method using sodium citrate-citric acid. In the electrolytic method using sodium citrate, i.e. neutral medium, the isolation of iron carbide depends on the condition of electrolysis remarkably.
  • Isolation and Separative Analysis of Iron Sulphide and Manganese Sulphide in Iron and Steel

    pp. 86-93

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    Study was carried out on extraction of sulphides in iron and steel and separative analysis of FeS and MnS in the extracted residues. For extraction of sulphides, the electrolytic method with constant potential and neutral electrolytic solution (5% sodium citrate, 1% potassium bromide, 1% potassium iodine) and at low temperature below 5°C was found to be most favourable.
    For the separative analysis of FeS and MnS in the extracted residues, the hydrogen reduction method was most favourable. FeS in the residue was reduced completely in about 2 hr in the stream of hydrogen at 800-900°C and the corresponding H2S was generated, on the other hand, MnS remained without change, even if the residue was a solid solution of FeS-MnS.
  • Study on Phase Analysis of Titanium in Steel

    pp. 94-104

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    In order to establish a method for phase analysis of titanium in steel, the chemical behaviors of various titanium compounds synthesized and those yielded in steel were investigated. Furthermore an investigation was made of the change in amount or form of the titanium compounds in steel by heat treatment.
    The experimental results were as follows:
    (1) Extraction of titanium compounds from steel was most favorably carried out by I2-CH3OH (10%) method. Extraction by HCl (1+1) showed a lower yield.
    (2) No change was seen in nitride, oxide and sulfide of titanium in steel by usual heat treatment.
    Titanium carbide, however, became soluble by heat treatment at about 1300°C, and reprecipitated by tempering.
    (3) As for the oxide form, only sesquioxide was formed in the steel specimens.
    (4) Titanium carbonitride could not be identified in the steels examined.
    (5) The procedure for phase analysis of titanium in steel is as follows:
    a) 1g of sample is decomposed by 100ml of I2-CH3OH (10%), under stirring, at room temperature and filtered.
    (Separation of metallic Ti)
    b) The extracted residue is treated in the 30ml of H2SO4(1+9) at 70°C for 20min and filtered again.
    (Separation of fine precipitates of carbide and nitride)
    c) The residue of b) is treated with 30ml of HCl (1+1) containing HF at 70°C for 20min and filtered.
    (Coarse precipitate of nitride is determined with the filtrate, and that of carbide with the insoluble residue)
    d) Metallic titanium is calculated by subtraction of combined titanium fraction from the total amount which is determined with use of a separate sample.
  • Effect of the Use of SiC-Added Fireclay Brick on Oxide Inclusions in the Bottom-Teeming Ingot

    pp. 105-115

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    In order to reduce the oxide inclusions originated from casting-pit refractories in case of bottom-teeming ingots, SiC-added fireclay brick was used instead of usual fireclay brick as casting-pit refractories.
    The effect of the use of these bricks on oxide inclusions was studied comparatively. Moreover, the effect of runner brick was investigated by the same method.
    The results were summarized as follows:
    1. It was recognized that the content of CaO and SiO2in oxide inclusions, the number of macroscopic inclusions appeared on the ingot surface were decreased by using SiC-added fireclay brick.
    2. It was observed that effect of the runner brick on oxide incluions should not be neglected.
  • Strength and Toughness Evaluation of a High Hardness Steel

    pp. 116-124

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    The strength and toughness of a low alloy steel (0.8% carbon), quenched from 850°C and tempered at various temperatures below 600°C, have been investigated by static and dynamic bend tests and static torsion tests. The effect of notch radius on bend properties has also been studied. The results obtained in this study are summarized as follows:(1) The plastic deflection in the static bend test or the impact value decreases exponentially with increasing the stress-concentration factor “α” at the notch root.(2) The appearance of low temperature temper brittleness is markedly affected by test methods, that is, it appears at relatively low tempering temperatures and the embrittlement is more clearly observed in unnotched dynamic bend or static torsion tests than in static notched and unnotched bend tests.(3) An optimum hardness is observed on the fracture strength versus hardness curve in both bend and torsion tests.
  • Blast Furnace Computer Control

    pp. 125-141

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    Readers Who Read This Article Also Read

    1. Energy Saving in Ironmaking Processes Tetsu-to-Hagané Vol.64(1978), No.13
    2. Mathematical Models of Blast Furnace Tetsu-to-Hagané Vol.69(1983), No.10
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  • Physical Properties and Structure of Slag Melt

    pp. 142-157

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  • Determination of Carbides in Steel by Isolation Method

    pp. 158-168

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  • Report of the BOF Oxygen-Line Instrumentation Sub-committee

    pp. 169-174

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  • Studies of Neutron Moisture Gauges

    pp. 175-181

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  • 抄録

    pp. 182-192

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