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

Tetsu-to-Hagané Vol. 43 (1957), No. 7

  • STUDIES ON THE SINTERING MECHANISM OF IRON ORE PELLET (II)

    pp. 691-695

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    In continuation to the previous research (Tetsu-to-Hagané, vol, 43, No. 5 1957, p. 619) the phenomena of sintering process of iron oxide pellet was investigated by use of new apparatus. And some kinetic considerátions were made on the sintering process and it was found that the W. Jander's equation on solid reaction,
    F=(1-3√1-x)(2)
    esactly had conformed to the experimental data.
    Deducting from these experiments and considerations, the authors distinguished the sintering process into two parts: i.e. the former was "film sintering" and the latter was "body sintering" at higher temperature, and much care should be paid to the former stage of practical pelletizing operations.
  • AERODYNAMIC CONSTITUTION OF OPEN-HEARTH FURNACE (V)

    pp. 695-699

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    The air-uptake not only connects the lower furnace with the upper furnace but also determines, in concert with the furnace head, the combustion in the furnace chamber by composing the type of air flow for the burner jet. The furnace head must be arranged from this point of view.
    The uptake flow is apt to be stronger in the pit-side than in the charging-side. Generally, the double air-uptake causes the unbalanced air flow and the deformed mixing situations. The single air-uptake is preferable for oil-fired open-hearth furnaces as it promotes air mixing under the burner jet.
    Model studies on the dimensions of the air-uptake in a single air-uptake design explained followings:
    (1) The uptake width shall be 50-60% of the chamber width, and it is securer to adopt 50%.
    (2) The uptake length shall be one-third of the chamber width.
    (3) The uptake width of the central uptake design shall be four-sevenths of the head width, while they are equal in the spread uptake design.
  • AERODYNAMIC CONSTITUTION OF OPEN-HEARTH FURNACE (VI)

    pp. 699-703

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    The furnace head is the portion between a furnace end and a throat, and its type gives the name of a design. It highly affects on the combustion in concert with the constitutions of the burner jet and air-uptakes.
    Model studies on the furnace head revealed followings:
    (1) The furnace chamber preferably shall be divided into two spaces balanced each other in front and back by the center line of the furnace head.
    (2) The standard dimensions of the single air-uptake furnace are given by following formulae.
    For the spread uptake type For the central uptake type
    Width: b=B'/2 Width: b2=0.88 B'
    Length: l=B'/2 Length: l1=0.88 B'
    Height:G=6B'/14.5 Height: G=6B'/14.5
    (3) The approaching side walls scarcely play the role of an accelerator of combustion but are apt to increase the wear.
    (4) The wear may be decreased without changing incoming air flow by declining the head roof or the end wall to the end.
  • THE HIGH TEMPERATURE STRENGTH OF LOW ALLOY STEELS

    pp. 703-710

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    Room and high temperature strength of some typical low alloy steels (Cr-Mo-V, Ni-Cr-Mo Ni-Mo-V, 1 Cr-Mo and 2.5 Cr-Mo steel) in steam turbine rotor shaft materials were studied.
    The results were summerized as follows: (1) The impact transition temperature in Ni-Mo-V and 1 Cr--Mo steel having a comparatively small hardenability lie on to moderately higher side. (2) Generally the higher the room-temperature tensile strength, the higher the tensile strength at high temperature for short time, but it is not apparent that this difference is small. (3) In 500-550°C range 1 Cr-Mo-V steel have the strongest creep-resisting strength and Ni-Mo-V, 1 Cr-Mo, Ni-Cr-Mo and 2.5 Cr-Mo steel beomes weaker in the aforementioned order. (4) 2.5 Cr-Mo steel have the most remarkable elongation and Ni-Cr-Mo, Ni-Mo-V, 1 Cr-Mo and 1 Cr-1 Mo-V steel is a little elongation in their order during the creep rupture test. 1 Cr-1 Mo steel have an elongation of 12-13 per cent and the others have an elongation of over 20 per cent after the creep rupture test. (5) Design curve and master rupture curve at 500°C in each steels have been obtained. (6) Carbide corgulation and spheroidization was not observed in the specimens after no loaded heating test but it was observed after creep rupture test. (7) The tensile test results at high temperature for short time were not always agree with test results of long-time creep rupture and therefore creep resisting properties could not be judged from the former.
  • ON THE MECHANICAL PROPERTIES AT ELEVATED TEMPERATURE AND PROPERTIES FOR OXIDATION IN SOME HEAT RESISTING STEELS OF FERRITE SYSTEM

    pp. 711-713

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    Heat-resisting steels of ferrite system have good machinabilities and are very inexpensive materials compared with austenite system heat resisting steels. In recent years, therefore it has been studied rapidly. The authors conducted laborious investigation on its quenching and tempering hardness, mechanical properties at elevated temperature, rupture strength, creep limit and resistance to oxidation of several heat-resisting steels of ferrite system. The informations on these characteristics, the authors believe, will surely be valuable as reference for all the users of these steels.
  • THE STUDY OF HEAT-RESISTING STEEL (XI)

    pp. 713-720

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    In this report, the effect of "warm-work" and the variety of microstructure during precipitation for warm-worked material on 16-25-6 alloy containing Ti or B were studied.
    There are three different compositions in the specimens. (#D1 #D2 and #D3) Sample #D1 contained 0.68% Ti, #D2 contained 1.86% Ti, and #D3 contained 0.085% B, based on 16 Cr-25 Ni-6 Mo alloy. The chemical compositions is shown in Table 1 in full detail.
    After forged to bars, these samples were solution treated at 1150°C for #D1 and #D3, and at 1200°C for #D2 for 1 hour. Then the tensile-test pieces were made.
    The warm working was made at 650°C by means of an Amsler's tensile-test machine.
    The ratio of work was arrived at by computing the ratio of reductioh of area in all parts. After measuring of hardness and microtructure, these ramples were annealed at 650°C or 750°C from 1 hour to 500 hours. Then the change of hardness and microstructure by precipitation were measured.
    The effect of Warm-working on strength of material of all samples of #D1, #D2, #D3 was ascertained by hardness measuring, even after annealing at 650°C or 750°C for 500 hours. The hardness of the warm-worked alloys after annealing at 650°C or 750°C for 500 hours was much higher than the hardness of the same samples only aged at same temperature for 500 hours without the working process.
    When the element Ti was added to, #D1 (0.68% Ti) and #D2 (1.86% Ti) almost similar changes occurred during testing. Althongh the warm-working effect was evident on #D1, #D2, two samples containing Ti showed much precipitation-hardening during heating whether they were warm-worked or not. But, sample #D3 containing B showed remarkable precipitation hardening only when it was warm-worked before aging. So the warm-working process was more effective on #D3.
    The abnormal microstructure which appeared during heating after warm-working was also discussed in the full report.
  • INFLUENCE OF CARBON ON THE PROPERTIES OF 18-4-1 TYPE HIGH SPEED STEEL

    pp. 720-725

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    To investigate the influence of the carbon on the properties of 18-4-1 type high speed steel which were used for cutting tools and hot dies, the authors measured the critical temperature, Ms point, quenched and tempered hardness, retained austenite, dimensional change, toughness and mechanical properties at high temperature.
    The results obtained were as follows:
    (1) The critical temperature and Ms point were lowered with the carbon content and the begining curve of the isothermal transformation was removed to right side with the carbon addition.
    (2) The quenched hardness was raised with the austenitizing temperature in the lower carbon content and was lowered as the carbon increased to more than 0.65%. For obtaining the fully quenched hardness, the austenitizing time needed about 2 minutes for 10Φ×10mm specimen. The tempering hardness as the secondary hardening was raised with the carbon and the quenching temperature.
    (3) The quantity of retained austenite measured by the magnetic method increased with the carbon addition, but by the sub-zero treatment it decreased to a little amount. During the tempering, the decomposition of retained austenite was occurred at about 500°C rapidly and all amount of them was entirely decomposed between 575°C to 600°C tempering.
    (4) The toughness measured by the static bending test decreased with the carbon addition and the hot impact strength also decreased with the carbon content. The tensile strength, elongation and reduction area were hardly affected by the carbon content, but were affected by the tempering and testing temperature.
  • STUDIES ON INDUSTRIALIZATION OF MT PERMANENT MAGNET (III)

    pp. 726-732

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    Fe-Al-C permanent magnet alloy, the products of which have been produced since 1947 under the commercial name of MT magnets, is the unique magnet alloy which possesses comparatively high coercive force of 200 Oersteds containing none of rare metals. In this report, there will be dealt with the results of experiments relative to industrial aspects which are believed necessary to be known by customers, with special emphasis on those basic magnetic properties and experimental data on demagnetization in additions to industrial applications.
    The essential magnetic properties are listed in Table 1. The residual induction of MT magnet is nearly equal to one of MK or NKS magnet and the coercive force is nearly equal to one of high Co steel. The stability of magnetic induction over extended period of time is very important in case of electrical instruments or meters. The magnetic aging may be due either to structural change and thermal fluctuation or to external demagnetizing influences such as stray field, mechanical shock, heating or change of reluctance. Effects of various demagnetizing factors on the magnetic stability were investigated accordingly.
    In all cases this magnetic change can be related to time and external actions in a logarithmic form. Magnetic aging will be stabilized by means of the previous demagnetizing of alternative field and heating. Thermal coefficient of this alloy for the watt-hour meter is -4.0×10-4/°C and is considerably larger than one of chrome steel.
    The application of this magnet to industrial fleld is now being expanded. Among its applications, some are now developed to commercial production with great success. The representative examples of industrial uses are mentioned. By the performance tests of MT and Cr steel for watt-hour meters, it was proved that MT is more stable against demagnetization and maintains higher magnetic flux even with its less weight.
  • INVESTIGATION ON ACID-RESISTANT HIGH-SILICON IRON (II)

    pp. 732-737

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    Already described in the previous report with the same title, Part. 1.
    (Refer to p. 652, June 1957 issue of Tetsu-to-Hagané)
  • ON THE PROGRESS OF IRON AND STEEL MAKING TECHNIQUE AT MURORAN WORKS

    pp. 738-744

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    Description was made on the outline of progress of iron and steel making technique at Muroran Works of Fuji Iron & Steel Co. Ltd. for about ten years since the end of war II.
    Particulary, the following new three practices on the operating method of the open hearth furnace and two studies on method of utilizing non-developed resources were explained:
    (a) Steel-making operation by using the coke oven gas under high pressure.
    (b) Recent practice of oxgen steel-making.
    (c) Steel-making operation with high pig ratio.
    (d) Study on the effective use of iron sand.
    (e) Study on the magnetizing-roasting of limonite.
  • SOME PROBLEMS ON HEAT RESISTING ALLOYS

    pp. 745-748

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    Recently the heat resisting alloys have made remarkable developments. There are few differences in the essential consideration of chemical constituents, but the aging time has been so prolonged that the stability of structure and strength at elevated temperature much increased. In heat-resisting alloys, some phenomena such as creep and fatigue take place under repeated stresses during practical use.
    The transformation and precipitation of the alloys are accelerated by these repeated stresses so that there occurs a change of the volume and a decrease in the creep or the fatigue strength.
    Further, a systematic research on these problems is needed. It is also presumed neccessary that new manufacturing techniques, for example, vacuum-melting, vacuum-casting and hotextrusion should be introduced for further improvements in heat resisting alloys.
  • HOW TO DEAL WITH IRREVERSIBLE PHENOMENA

    pp. 749-755

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  • 抄録

    pp. 756-760

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  • 鉄鋼ニューズ

    pp. 761-761

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  • 国内国外刊行誌参考記事目次

    pp. 762-765

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