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

Tetsu-to-Hagané Vol. 58 (1972), No. 1

  • 1971 Perspective of Production and Technique of Iron and Steel in Japan

    pp. 3-17

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  • Prediction of Blast Pressure Change by a Mathematical Model

    pp. 18-28

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    Simulation of a blast furnace by a mathematical model is one of the means, by which the phenomena in the blast furnace, especially in the high temperature zone, are quantitatively understood. The means described are as follows;taking account of the dead man, the blast furnace from top of bed to tuyere level is devided into five parts, i. e., indirect reduction zone, smelting zone, direct reduction zone, tuyere zone and race-way zone. In each zone the twelve simultaneous ordinary differential equations, consisting of the heat transfer and reaction rate equations, are set up. Rate equations of six kind of chemical reactions and the equations concerning the flow of fluids, which are expected to occur in the blast furnace, have been obtained experimentally. Furthermore, a few parameters are determined, so as the computed curves of pressure drop and temperature to agree with those measured in a actual large blast furnace.
    In a actual furnace, it occurs sometimes that the blast pressure increases abnor mally, and then the state of the furnace becomes worse and finally serious. As the results of analysing such case by the use of the mathematical model, the increase of the blast pressure can be predicted before about three hours.
  • Kinetics of Decarburization of Liquid Iron at Low Concentrations of Carbon

    pp. 29-40

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    The present paper deals with a kinetic study of decarburization of liquid Fe-Ca lloy in CO-CO2 atmospheres at 1 600°C. The study has been especially directed towards determining the rate-controlling steps at low carbon contents of the melt.
    In the concentration range above 0.05%C, the rate of decarburization is influenced by the gas flow rate.
    It is shown that at carbon content higher than 0.1-0.15%, the decarburization controlled by gaseous diffusion.
    In the concentration range below 0.05%C, the rate of decarburization no longer depends on the gas flow rate, if it is higher than 1 300cc/min. The views on the mechanism of decarburization under this condition are summarized as follows;
    (1) The decarburization by blowing gas of the ratio pco, /pco below 1/4 is controlled by chemical reaction.
    The rcactions conceived here are;C+CO2k1→k1′2CO3, CO2k2→k2′CO+O, C+Ok3→k3′The results can be explained reasonably well by postulating appropriate values for k2, k3′, k1′/k3′.
    (2) At higher gas ratio (Pco2/Pco≥1/4), the rate-determining factor changes gradually.It is shown that at pco2, /pco≥7/3, the decarburization is controlled by the mass transfer of carbon in liquid iron, themass transfer coefficient being 0.036cm/sec.
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    Readers Who Read This Article Also Read

    1. Kinetics of Decarburization of Liquid Iron with High Concentration of Carbon Tetsu-to-Hagané Vol.57(1971), No.9
    2. Kinetics of Decarburization of Liquid Iron by Ar-CO2 Gas Mixture Tetsu-to-Hagané Vol.58(1972), No.12
  • Effect of Sulfur on Solidification of Rimming Steel

    pp. 41-59

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    With intent to make clear the effect of sulfur on the solidification of rimming steel, the properties of low sulfur rimming steel ingots were examined and were compared with that of standard rimming steel ingots.The characteristics of low sulfur rimming steel ingots were summarized as follows:
    (1) The number of the elongated blowholes diminishs and the thick solid-skins develope, but some skin holes are formed.
    (2) Plenty of MnO (FeO) inclusions are precipitated on the inner surface of blowholes.
    (3) Carbon contents of ingots are low in comparision with that of liquid steel in ladle.Sulfur contents of ingots are very low as was expected, but the segregation ratios are rather high.
    (4) Sulfide inclusions decrease and oxide inclusions slightly increase, while gross inclusions exceedingly decrease.
    These characteristics of low sulfur rimming steel ingots are attributed to the C-O reaction, the fluid motion and the surface tention of liquid steel in mold.
  • The Behavior of Oxide Inclusions in the Solidification Process of Steel ingot

    pp. 60-75

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    It was found that a large number of inclusions with various sizes were suspended in a molten steel taken from a tapping ladle and the number of fine inclusions did not decrease by killing for about 20 min. The chemical composition and the number of these inclusions were determined.The distribution of inclusions in the bottom half of 7 ton ingots was inverstigated, taking above results into consideration. In particular, diffusion growth mechanism was applied theoretically for the growth of inclusion in the negative segregated zone of these ingots.
    Observation of macroscopic inclusions, which appeared in the negative segregated zone of a 90 ton ingot, indicated that the formation of the inclusions was closely related to the solidification condition in the region.
  • A Model Study on Jet Penetration and Slopping in the LD Converter

    pp. 76-84

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    A simulation study was made of the jet penetration and the splashing of molten materials due to oxygen jet (slopping or spitting) in the LD converter.
    By investigating the relations among the blowing conditions, the penetration depth and the splashing height, empirical formulas for these relations that are applicable to large scale apparatus were derived.
    From the results of this study, an equation for estimating the penetration depth in the actual LD furnace and some knowledges useful for realizing the physical characteristics of slopping and spitting were obtained.
  • Shape Factor of Calibers in Rolling of Structural Sections

    pp. 85-92

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    A new equivalent rectangle method has been developed and the factor depending on shape of sections has been determined in caliber rolling of structural sections. To confirm the correctness of this method, the calculated results of ratio of torque/force in various calibers have been compared with those obtained from measurements of roll force and power. It may be applied with sufficient accuracy for calculation of roll force and power. For a condition of the practical hot rolling, the following values appear to give the best results: average coefficient of friction μ=0.15, average angle of friction cosφ=0.65, efficiency of deformation η=0.35, average lever arm ratio λ0=0.37.
    x

    Readers Who Read This Article Also Read

    1. Industrial Instrument Standard in the Iron and Steel Industries Tetsu-to-Hagané Vol.57(1971), No.12
    2. On the Dissolution Process of Deoxidizer into Molten Iron and the Mechanism of Formation of Oxide Inclusions Tetsu-to-Hagané Vol.57(1971), No.13
    3. Studies of6%Nickel Steel for Low Temperature Use Tetsu-to-Hagané Vol.58(1972), No.1
  • Effects of Carbon Content on Primary Recrystallization Texture in Fe-Al-N Alloys

    pp. 93-106

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    Fe-Al-N alloys investigated contained<0.005%, -0.06% Al, <0.002%-0.02% N and 0.001%-0.04%C. Effects of C content on primary recrystallization texture, A1N precipitation, grain size and drawability in these alloys were studied.
    With increasing C content, the amount of grains with {111} lattice plane parallel to the sheet plane decreases, the main component of primary recrystallization texture changes from {111}‹110› to {554}‹225›, grain size decreases, grain shape changes from the “pancake” to the equiaxial type, and thedrawability markedly decreases.
    These effects of C content on various properties of Fe-Al-N alloys are rather inconspicuous for the C content up to 0.01%but become extremely remarkable when it exceeds 0.01%and are explained by the effect of C content on AIN precipitation during precipitation treatment prior to cold rolling and during heating to (and at) the annealing temperature.
  • Oo Structural Diagram of Austenitic 25%Cr-20%Ni-Fe-C Type Alloys

    pp. 107-118

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    To establish the structural diagram of 25%Cr-20%Ni-Fe-Calloys in which carbon content is lower than2.4wt%, were studied thermal characteristics such as melting temperature, carbide solubility in austenitic phase, and stability of carbides and sigma phase. In addition to the sectional diagram shown in Fig. 16 in the text, the remarkable results are as follows.
    (1) The solubility of M23C6type carbide in austentitc phase is shown by where C is the carbon content (wt%) in solid solution and T the absolute temperature
    (2) Sigma phase precipitates within austenite phase in the alloys of lower carbon content. On the other hand, in the case above about 0.25%C, it is likely that M23C6type carbide transforms to sigma phase.
  • Effect of Ni on the Behavior of Austenite Grain in Ni-Cr-Mo-V Steels

    pp. 119-127

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    In relation to the fact that Ni-Cr-Mo-V Steels containing 3 to 4%Ni have a tendency to form coarse austenite grains, an investigation was made on the effect of Ni on the behavior of austenite grains in this kind of steel.
    Four materials of a fixed chemical composition except for Ni content which was varied in the range from 0 to 4.5%were prepared. Specimens which have martensitic structure obtained by preliminary quenching from 1250°C were heated to 900°C. Austenite grain size at 900°C and structural changes during heating in these specimens were observed.
    It was found that austenitie grain size tend to become coarser with increase in Ni content. Further, it was known that acicular austenite grains which were formed in early stage of austenitization became finer and more stable with increase in Ni content.
    Based on these results, considerations were made on the austenitizing mechanism of steels which have acicular prior structure.
    It seems reasonable to consider that coarse equiaxed austenite grains are formed as a result of preferential growth of a small number of acicular austenite grains.
    It is believed that the role of Ni in formation of coarse austenite grain in Ni-Cr-Mo-V steels is to make the lattice orientation of acicular austenite grains uniform, and, consequently to increase the stabilization of acicular grains, this being a necessary condition for preferential growth of a small number of these grains.
    x

    Readers Who Read This Article Also Read

    1. なんとかしてもらいたい三つの問題 Tetsu-to-Hagané Vol.64(1978), No.5
    2. Nucleation Sites of Austenite from Lath Martensite in Fe-0.2%C-X Alloys Tetsu-to-Hagané Vol.64(1978), No.5
    3. Reverse Transformation of Low-carbon Low Alloy Steels Tetsu-to-Hagané Vol.60(1974), No.2
  • Studies of6%Nickel Steel for Low Temperature Use

    pp. 128-141

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    Studies were made in connection with the development of a new steel for low-temperature use.The ef-fects of alloying elements on the toughness of6%Ni steel were examined in relation to metallurgical factors such as temper brittleness, microstructure and the stability of temper-formed austenite (reverted austenite). The results are as follows:(1) The addition of manganese refines the microstructure and improves toughness but promotes susceptibility to temper brittleness.(2) The addition of molybdenum or tungsten is bene ficial in preventing temper brittleness of6%Ni steel with a high manganese content and in producing finely dispersed and stable austenite islands, but has the disadvantage of retarding recovery on tempering.(3) The addition of chromium is useless in improving the toughness of 6% steel.(4) The addition ofcopper has similar effects to those of manganese, that is, it refines the microstructure and improves toughness.
    Based on these results, a new steel has been developed with 6%Ni, 1-2%Mn and 0.2%Mo or 0.45%W, which has good toughness, such as 13kgm at-196°C.
  • The Determination of Boron Nitride in Steel by Means of Infrared Spetrometry

    pp. 142-150

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    A rapid and sensitive infrared spectrometric method is described for the determination of microgram quantities of boron nitride in steel. An infrared absorption spectrum of boron nitride (BN) is characteristic and sensitive as reported by Ohiko Kammori and others, by whom a very successful method for the determination of BN in steel has been proposed.
    In this study further improvements were made by employing the procedure of the incineration of the residues, that is, the recovery of BN on filter became complete and very little effects of other chemical compounds (carbides, filter, etc.) were observed.
    0.5 to 1.0g of sample is dissolved with 50ml of H2SO4 (1+6) in a 200ml beaker, then the solution is filtered with fine pore size filter as used for BaSO4 filtration. The residues on filter paper in a crucible is heated very gently with small flame of burner until all the paper is reduced to carbon without taking fire, then incinerated in electric furnace at 500°C for 20 minutes.The resulting residues mixed with 300 mg of KBr for about 15 minutes in agate motor is prepared into a pellet of 13 mm in diameter. Absorbance measurements of the characteristic BN band at 1380-1 cm are made by the base line method. The minimum detectable content of BN in steel was 0.0001% and the calculated values as B agreed to the acid insoluble B content.
  • End Point Temperature Control of Basic Oxygen Converter by Sub-lance

    pp. 151-157

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    A new end point temperature control system introducing a sublance has been developed in Steelmaking Plant-II (nominal capacity: 100t×2, 110t×1), Muroran Works, Nippon Steel.
    The main body of the sub-lance is a water-cooled steel pipe (2-1/2, O. D.) which moves up and down vertically along the guide rail. The sensor attached to the tip of the lance is a consumable immersion thermo-couple of the same type as that used in the turn-down temperature measurement.
    By using the sub-lance, the bath temperature can be measured without stopping the oxygen blow, and “dynamic end point control” has thus become possible. Of every heat, the sub-lance starts to measure the bath temperature at 350 Nm3 (one minute) prior to the calculated total oxygen, and the rising temperature curve is modified accordingly.
    Since September 1968, when it was made operative at No3 vessel, the sub-lance has been working quite satisfactorily.
    As the result:
    (1) The end point temperature control (±10°C) was improved by 15-17% reaching 87% of the on-temperture rate.
    (2) Consequently efficiency in steelmaking was improved markedly, and in April 1970 the plant established a world record of 2 762 heats per month.
  • Petrographic Studies and Its Utilization of Coal for Coke Making

    pp. 158-179

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  • Testing Method of Vanadium Pentoxide Attack of Steels

    pp. 180-201

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  • On the Universal Decimal Classification Explanation of the UDC

    pp. 202-207

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  • 抄録

    pp. 208-216

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