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

Tetsu-to-Hagané Vol. 48 (1962), No. 13

  • 学協会への弁

    pp. 1639-1640

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  • Study on Reduction of Iron Sands by Waste Gas from an Electric Furnace on the Fluidized Bed

    pp. 1641-1646

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    Studies were made on prereduction of iron sands by utilization of the top gas from an electric arc furnace. The reducing furnace was a two-stage fluidizing roaster. The upper stage was an oxidizing bed, while the lower stage was a reducing bed. The results obtained were as follows:
    (1) Iron sands were reduced in batch operations. When the reducing gas was composed of 760% CO, 164% CO2, and 7.6% H2, the time for 50% reduction was about 180 mn at 900°C. When the gas contained CO 97-98% and CO2 2-3%, it took about 90mn for 50% reduction.
    (2) Continuous operations with the two-stage fluidizing roaster was very satisfactory. When the average holding time on the lower bed was about 360 mn in a reduction by a gas containning 76% CO, 164% CO2, and 7.6% H2, the degree of product of reduction was about 50% and the utilization degree of gas was only 4%. When the gas was composed of 97-98% CO and 2-3% CO2, a reduced are with the reduction degree of 60-70% was continuously produced. In this case, the average holding time was about 180 mn and the utilization of gas was increased to 9-10%.
  • Sulphur Partition between Slag and Bath during Melting Process of Stainless Steel

    pp. 1647-1654

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    Taking slag-metal samples at various working periods, (i.e. before slag-off, before tap and in ladle) during melting process of stainless steel in a 30-t basic electric furnace, sulphur partition at each period was examined.
    Following results were obtained:
    1) The sulphur capacity Cs, i.e. (% S) /a [s] [%Si] 1/2 at each period was greater, the higher the molar basicity, which was defined as N2cao/Nsio2.
    2) The sulphur capacity Cs was increased linearly with decreasing amount of Cr2O3 at he constant N2Cao/NSio2. t
    It was considered that the higher the Cr2O3 in slag, the smaller becomes the slag-off Cs ven in the case when the slag indicated the same value of Vm'-NCao.
    3) Though the effect of MgO content of slag on Cs was rather unobvious as compared with (Cr2O3), it was recognized that the sulphur capacity Cs was increased with increasing amount of MgO at the constant N2CaO/NSio2 and Cr2O3 content.
    4) The sulphur capacity, except in ladle, was correlated statistically with the main slag composition as in the following equation:
    Covering the temperature range 1540 to 1680°C,
    log [ (%S) /a [s] [%Si] 1/2] =0. E867 log [N2CaO/ (Nsio2 + Ncr2O3)] -0.723
    5) The sulphur capacity C's, i.e. (%S) (NFeO) /a [s] was less closely related to
    N2CaO/ (NSiO2 + NCr2O3) than Cs was.
    6) The logarithm of sulphur capacity Cs was increased linearly with increase of the excess base, i.e. n CaO- (n SiO2+ n Cr2O3).
    No advantage were obtained in replacing the basicity term, i.e. N2CaO/NSiO2+NCr2O3, by the excess base.
    7) The logarithm of (Cs (NSiO2+NCr2O3) /N2CaO) was a linear function of the reciprocal of absolute temperature.
    The following equation was statistically obtained:
    log (CS (NSiO2+ NCr2O3) /N2CaO) = 3040/ T + 0.704.
    8) The sulphur content in pit sample was increased rapidly, with increase of the value of NFeO (NSiO2+NCr2O3) N2CaO of the final slag composition, if it exceeded above 16×10-2.
  • Change in Compositions of Various Metals before and after Consumable Electrode Arc Melting

    pp. 1654-1659

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    In order to study the refining process by the consumable electrode arc melting method, many kinds of metals such as carbon steels, low-alloy steels, bearing steels, stainless steels, heat-resistant alloys, magnetic alloys and titanium are melted by this method, and analyses of chemical components and oxide inclusions are carried out with the materials before and after the consumable electrode arc melting, that is, with the electrodes and the ingots.
    The results obtained were as follows:
    By the method every oxide content in various steels and alloys was decreased, which resulted in a decrease of the oxgyen content as much as by 50% of that of electrode. In the metals containing more or less Al, the Al2O3 was decreased mainly; and in the steels scarcely containing Al, the MnO and the SiO2 were mainly decreased. The decrease of nitrogen content, being not so markedly as of oxygen content, was as much as by about 30%. In the alloying elements, the content of Mn was decreased as much as by about 30%.
  • On the Nonmetallic Inclusions of a Bearing Steel Treated with Acidic Slag

    pp. 1659-1666

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    It is interesting that when molten steel has been treated with various synthetic slags, the latter is presumed to have some effect on the nonmetallic inclusions and the steel quality.
    A bearing steel (C1.04, Cr1.5%) treated with synthetic acidic slag (A) was compared with a non-treated similar steel (B) with respect to inclusions and steel qualities. The deoxidizers used are Al, Al+ Ca-Si and Ca-Si.
    The steel (A) contained more oxygen than the other steel (B), but with respect to the chemical composition, cleanliness, results of sand mark test and macro-etch test, both (A) and (B) were almost equal.
    There were found elongated inclusions (A-type) in a bearing steel added with deoxidizer Ca-Si and treated with acidic slag. An examination of the inclusions by transmission electron diffraction showed that the inclusions consisted of a-tridymite or fayalite.
    Therefore, the elongated inclusions in steel (A) presumably consisted of FeO-Si02 system.
    Thus the aforementioned on the treatment of molten steel with synthetic slag evidenced that the slag treatment would control nonmetallic inclusions in steel.
  • Gauge Variations Of Strips Causedby ROUingLarger Slabs

    pp. 1667-1673

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    Slabs tend to become larger and larger for improving the rolling capacity and the yield. In paralled therewith, the gauge and quality of the strip coil are susceptible to variations and would give rise to discussions on the equipment.
    Gauge variations alone are discussed here. There are many factors which cause gauge variations. When larger slabs are rolled, however, it is the variation of deformation resistance due to a temperature difference that mainly causes gauge variations.
    As the thickness of a bar leaving the rougher is 3/4-1 nch, the larger slab becomes the longer bar on the delay table. The temperature difference between the top and the tail of the bar is larger and causes the gauge variations owing to the mill spring. These gauge variations are due to a difference of rolling speed between the rougher and the finisher.
    If the roughers are composed of two stands and the rolling speed of the last roughers is controlled in proportion to the finisher, the temperature difference is reduced without spoiling the roping capacity.
    Skid marks too tend to become larger. In order to reduce the skid marks, it is effective both for design and opperation of a furnace to make the heat-liberating distribution as higher as possible on the charging side of the slab-reheating furnace.
  • Quenching Ability of Spray Quenching on the Inducdtion Hardening

    pp. 1674-1678

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    The hot junction of Pt-Pt. ERh couple was fixed at the centre of a 10mm Ag ball. After heating up to 800.. this ball was dropped into a spray of various quenching media and the cooling curves were plotted by oscillogram. From these data, the spray-quenching mechanism was considerd.
    As the result, the next conclusions were summarized.
    (1) The spray-quenching mechanism is similar to that of th conventional quenching essentially, but the cooling rate at the each stage of cooling curvebecomes larger. In particular, vaper-film-breaking temperature rises extremely.
    (2) The quenching ability of oil emulsion was compared with that of water.
    (3) The effect of the flow rate on the cooling curve in spray quenching was made clear,
  • Study on the Isolation of Oxide Inclusions from Steel

    pp. 1679-1684

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    (1) In order to separate the oxide inclusions in carbon steel, such as aluminium-silicate, manganese-silicate or a alumina, the sample of steel is treate electrolytically in a neutral electrolyte and this residue is treated by chlorination method, and by this process, the oxide inclusions can be isolated fully. By chemical analysis of these oxide inclusions isolated, the quantities and chemical content of each oxide of various types can be known.
    The shape and structure of oxide inclusions are examined after heating these residues at temperature between 500°C and 800°C in the air atmosphere and burning the amorphous carbon formed by the decomposition of the carbide during chlorination.
    (2) Alcohloic-iodine method is applicable with satisfactory performance to the isolation of oxide inclusions, such as (Fe, Mn) O.Fe2O3 and (Fe, Mn) O, from the rimmed steel.
    (3) In the case of isolation of oxide inclusions from high-Cr-Ni alloy-steels by electrolytic-and chlorination-method, the hydrated silica is formed by chemical reaction between ionic silicon and electrolyte.
    This hydrated silica can be satisfactorily separated without decomposition of oxide inclusions by using 2.5% or 5.0% NaOH solution from the residues isolated electrolytically.
  • Relation between Fundamental Researches and Practical Process in Steelmaking

    pp. 1685-1691

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  • On Treatment of the Blast into Blast Furnaces

    pp. 1692-1699

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  • 日本学術振興会製鋼第19委員会 (第1分科会) 報告

    pp. 1700-1705

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  • 抄録

    pp. 1706-1710

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  • 鉄鋼ニューズ

    pp. 1714-1715

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  • 特許記事

    pp. 1717-1720,1710

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