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

Tetsu-to-Hagané Vol. 47 (1961), No. 2

  • 北陸の大雪に想う

    pp. 109-110

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  • On the Rate of Carbon Oxidation in Liquid Iron by Oxygen Blowing

    pp. 111-115

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    The rate of carbon oxidation is measured by blowing the oxygen gas into liquid iron. The reaction can be written such as
    C+1/2O2(g)→CO(g).
    The observed rate against the flow rate of the oxygen gas shows that the oxygen gas supplied is completely consumed in the case of all flow rates. Therefore it may be emphasized that the rate of chemical reaction which may occur on the interface between liquid iron and gas phase is sufficiently rapid to be settled by a supply of reacting species. Furthermore, the constant rate of carbon oxidation observed at high oxygen pressures may be due to the fact that the rate-determining factor exists in the transfer of reactants (carbon) towards the surface where a chemical equilibrium occurs.
    These experimentsl results may be explained by theoretical considerations carried out on the basis of the diffusion film theory.
    The total amount of carbon taken away from liquid iron at high oxygen pressures is calculated by
    _??_
    where ρ is the density of liquid iron, Dc, the diffusion constant of carbon in liquid iron, Δl the thickness of diffusion film, and n, the number of bubbles.[C] li, and [C] ni are the respectiveinitial weight% of carbon in the first and n-th bubbles.[C] Ω is the surface% of carbon. Calculated results are qualitatively in agreement with the observed data.
  • On the Mechanism of Evolution of Inner Cracks of Cast Billets

    pp. 116-124

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    In the second report of this series, the effect of the secondary cooling on a cast billet was studied and it was revealed that too-intensive spray cooling and too-high casting temperature induced inner cracks of billets (ib., Tetsu-to-Hagane, vol.46, 1960, No.7, p.753). In this report the mechanism of the evolution of inner cracks of cast billets was investigated.
    The mechanism of the evolution of cracks of cast billets is essentially the same as that in normal ingot casting. In continuous casting, however, one must not neglect the effect of relatively intensive spray cooling and pinch rolls on the evolution of cracks.
    At the time of passing through the pinch rolls, internal stress which consists of thermal stress originated from intensive spray cooling and mechanical stress originated from pinch rolls may become to be greater than the strength of billet. That is, the inner cracks may occur. And this inner cracks will be terminated by molten steel which is still remained in the core of billet.
    Calculation revealed that internal stress of a billet had the possibility to be greater than the strength and experiments revealed that the end point, the time of evolution, the selective direction, macroscopic and microscopic characteristics of inner cracks substantiated this mechanism of the evolution of inner cracks.
    And the experimental results in the second report can be explained by this mechanism of the evolution of cracks.
  • Ball-Bearing Steels Made from the Sponge Iron as Raw Material

    pp. 124-129

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    Nowadays, there are many reference data on the ball-bearing steels pertaining to the melting, refining, forging, hot-working and heat-treatment, but few reports on the raw material for melting.
    In the SKF ball-bearing steels, the sponge iron and returned scrap have been used as the raw materials, while the iron sand, the commercial and returned scrap have been used generally in Japanese ball-bearing steels.
    Therefore, it is very interesting to ascertain what the sponge iron has the effect on an improvement in the durability of ball-bearing steels.
    In this report, the austenitizing behaviour and durability of ball-bearing steels, made from the sponge iron in a basic electric arc furnace, were studied by means of chemical anaalysis, point-counting, lineal analysis, the Rockwell hardness test, static torsion test and thrusttype life test.
    The results obtained were as follows:
    (1) The minor impurities like copper, molibdenum and tin were decreased considerably in steels, in which more than 50% of the sponge iron was charged in the ratio of more than 50% of the raw material.
    (2) As the charged ratio of the sponge iron was increased, the contents of stringer-type and oxide-type non-metallic inclusions showed a rising tendency, but that of Al2O3-type non-metallic inclusions showed no change.
    Total content of non-metallic inclusions was increased with the enhancement of the charged sponge iron.
    (3) In each specimen the mean diameters of the spherodized carbide were between 0.84μ and 1.04μ, and this size appeared to be larger considerably than that of the SKF and the New Departure ball-bearings.
    (4) The behaviour of carbide solution into austenite showed no difference in each specimen except No.2, of which carbide did not go to solution easily at an austenitizing temperature of 840° on account of 0.2% vanadium addition.
    (5) Three groups were divided by the results of life test. Especially the best group was No.3 (50% sponge iron+50% returned scrap) and No.6 (all sponge iron), the second group was No.2 (50% scrap+30% returned scrap+20% iron sand+0.2% vanadium), No.4, (50% iron sand+50% sponge iron) and No.5 (25% returned scrap+75% sponge iron), and the last group was No.1 (50% scrap+30% returned scrap+20% iron sand), which showed the commercial charging ratio of the raw materials.
  • Study on the Spangle in the Hot-Dip Galvanized Coating

    pp. 129-133

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    The investigation dealt with the influence of aluminium, and tin additions on the spangles (flowers of zinc) on galvanized coating which are of commercial importance because of theirpleasing and aesthetic appearance. The spangles of the galvanized coating produced byusing the elecrolytic-grade zinc baths and the electrolytic zinc baths contained with 0.5w/oor lower aluminium content were formed the grain-shaped spangles with a weak contrast.On the other hand, the spangles of galvanized coating, by using an electrolytic zinc bath withabout 0.1w/o or higher tin concentration, resulted in the larger and regular spangles with afeathering aesthetic appearance.
    It was possible to find a satisfactory explanation for such influence of nucleation of spanglesas function of coating time gives a similar shape to the formal frequency of nucleous formationas a function of supercooling. The macro- and microscopic growth of spangles werefound to have the linear rate.
  • Effect of Several Factors on Embrittlement of Solid Metals in Contact with Liquid Metals

    pp. 134-139

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    Embrittlement of mild steel in contact with molten copper or copper-tin alloy or zinc-tin alloy, and embrittlement of tin or lead in contact with mercury were examined.
    Several factors affecting embrittlement became clear as follows. In general, embrittlementof this kind, namely fracturing by penetration of liquid occured severely at a comparativelylow working speed, but hardly at an impact working speed.
    Embrittlement of cold-rolled steel under the recrystalization temperature becomes lessliable to occur as rolling reduction increased, and the cracks run along strained ferrite-grainboundaries.Fine-grained lead was not embrittled by mercury, while coarse-grained lead was embrittledby mercury. The coarse-grained lead, however, did not show any brittleness in air.
    Fracturing by penetration of liquid occurred only by the stress at a difinite value, anddid not occur by a lower stress. This was shown by the constant tensile load tests of tinin mercury.
  • Change in Physical Properties during Tempering of Gamma Type Fe-Co-Cr-Ni Base Heat-Resisting Alloy, LCN-155

    pp. 139-145

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    The tempering process of the solution-treated γ type heat-resisting alloy consisting mainly of Fe, Co, Cr and Ni, and the effects of solution-treating temperatures and the additional elements (C, N, Mo, W and Cb) on its process were investigated by measurements of dilatation, specific heat, electrical resistance, and hardness.
    These results were summarized as follows:
    1. The tempering process of this alloy quenched in water from an elevated temperature was divided into two distinct stages about at 500°C and 750°C.
    2. At the first stage, an increase of electrical resistance, an evolution of heat, a contraction of the length, and no marked change of hardness were observed. It was considered that the change in properties during the first stage of tempering was not due to a precipitation of carbide or nitride but due to an unknown change in the Fe-Co-Cr-Ni quaternary alloy containing of no additional elements.
    3. At the second stage, a decrease of electrical resistance, an evolution of heat, a contraction of the length, and remarkable change of hardness were observed. The change in properties during this second stage of tempering was obviously due to the precipitation of carbides, nitrides, and intermetallic compounds. The amount of these precipitates and the velocity of precipitation were remarkably affected with the additional elements and the solutiontreating temperatures.
    4. It was considered that the change of the first stage advanced in processes as follows:
    Room temp.500°C 650°C °
    In quenching states ……A→A→A→A→A650 A: A stable state at high temp.
    In quenching states …_??_A': A stable state at low temp.
  • Spectrochemical Determination of Small Amount of Aluminium in Steel

    pp. 145-152

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    The determination of total aluminium in steel is of essential importance because of its vital basis decisive to a series of problem on structure and composition of steel.
    A spectrographic analysis applicable to the minute total aluminium (0.005-0.100%) in steelwas established as given hereinunder by means of a combination use of a medium sized quartzspectrograph and a grating spectrograph of Ebert type with an AC intermittent arcsource unit.
    Precision in the term of coefficient of variance attained to 3-5%, while accuracy thereofshowed quite comparable to results obtained by wet chemical analysis.
    Austenitic grain size was able to be proved by this method in a few hours after ingotmakingwhich was distinguished to ensure the quality of products.
  • Recent Problems on Automobile Steels

    pp. 153-162

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  • Observations on Industries in U. S. S. R.

    pp. 163-169

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  • Iron and Steel Situations in The People's Republic of China

    pp. 170-172

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  • Present Status of Iron-Base Powder Metallurgy of the World

    pp. 173-178

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  • 抄録

    pp. 179-182

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  • 鉄鋼ニューズ

    pp. 183-184

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