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

Tetsu-to-Hagané Vol. 43 (1957), No. 1

  • THE THEORETICAL LIMITATIONS OF THE BLAST FURNACE OPERATION

    pp. 3-11

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    Concerning this subject the author made public an article in the April 1942 issue of Tetsu to Hagané Because. in recent years, however, remarkable improvements have been carried out in the fields of coke, raw materials and operation methods of blast furnaces, the authors took up the same problem and obtained the undermentioned figures of limitation value of the blast furnace after a serie of experiments performed with the presènt raw materials.
    Assuming that coke ash is 12%, the mean value of Fe in the ore 57% and the blast temperature 700°C and the top gas is to be utilized up to 750 kcal, the blast furnace operation limits shall be 920 tons of pig iron per day, the coke ratio 0.585 and the blast 1000m3/min. The most economical and efficient Fe reduction under these conditions was achieved when gas (indirect) reduction was 70%, and direct reduction 30%. Also the amount of CO2 and CO in top gas was 17.5% and 24.1% respectively, and the ratio of CO against CO2 was 1.38. These figures, the present author learned, were the minimum limits in gas utilization.
    It is further to be added that the above-obtained results are not final, but vary with the different grades of coke, ore and operation methods used.
  • THE IMPROVEMENT IN PROPERTIES OF MOLTEN IRON (IV)

    pp. 12-17

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    One of the authors reported1) that by the O2 blowing treatment into molten iron the properties of the iron were improved, and moreover it was supposed that the O2 blowing treatment was suitable for producing the following cast irons; (1) direct castings from blast furnace molten iron, (2) cast iron contained various C and Si contents from cupola molten iron, (3) high strength cast iron, malleable iron or cast steel.
    So, in order to obtain the reference data for these above applications, the tests of O2 blowing treatment into cupola molten iron of 450kg, contained high C (3.7-`3.8%), were carried out three times. From the experimental results, it was made clear that the more rapidly the temperature of molten iron increased by O2 blowing and the higher the temperature of iron reached was, the more easily the decaburization proceeded. Cast irons added with the proper amounts of Fe-Mn, Fe-Si and Ca-Si, alloys after O2 blowing showed the properties of high strength, less mass effect and high heat-resistance in comparison with the iron without O2 blowing treatment.
    As tho O2 blowing treatment increased the temperature of molten iron and decreased easily the contents of C and Si in the iron, the treatment was suitable for the manufacture of high strength cast iron. For instance, by the inoculation with Ca-Si alloy after O2 blowing into the iron of C 3.4%, the cast iron showed about 38kg/mm2 tensile strength.
  • OPEN HEARTH FURNACE OPERATION BY THE COLD COKE OVEN GAS UNDER HIGH PRESSURE

    pp. 17-23

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    The open hearth furnace of Muroran Works was originally designed as of the Friedrich Type using mixed gas as fuel. But after the end of War II they were remodelled to the burner type, as required by the fuel situations at that time and the technical studies.
    There after those furnaces have beeen using both cold coke-oven-gas and liquid fuel up to the present time, during which period introducing the use of coke-oven-gas under high pressure into the operation.
    Various studies have been made on the method of utilizing this fuel.
    This report outlines, the situation when operation using low pressure gas was altered to do with high pressure gas, the study on the operating method in using high pressure gas as well as a few problems of the open hearth furnace using high pressure gas.
  • PRACTICAL INVESTIGATION ON WORK ROLLS FOR COLD ROLLING

    pp. 24-28

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    Forged steel rolls for 4-high cold reversing mill (work roll dia. 16 1/2") were practically investigated on the standpoint of roll users. The authors checked the hardening depth curves of work rolls (about 200 rolls) for several years by Shore hardness tester.
    These curves were estimated by their individual rolling condition, that is, production tonnage, difficulties of rolling operation, quantities of surface cracks during operation, etc.
    As a conclusion, the hardness depth curves of bad rolls have a different type from that of good rolls. These bad rolls extremely softenat the point of 5-`6mm from the original roll surface.On the other hand, the hardness of good rolls decrease linearly from their surfaces. Then, the authors investigated the surface structures of rolls by means of electron microscopic method, and could classify them in the following three groups.
    A group: martensite matrix+0.5-2μ cementite particles.
    B group: martensite matrix. with net structure+cementite. particles.
    C group: No cementite particle structure (martensite and austenite.)
    The authors compared these structures with their practical rolling results. B and C groups, especially C group, were not suitable for good rolling operation. Furthermore, both structures before rolling and after rolling on the same position of the roll were checked. Each group of roll structures has not been changed to another group during rolling operation
  • ON THE EFFECT OF WORKING VELOCITY ON THE STORED ENERGY OF COLD WORKED ARMCO IRON

    pp. 28-31

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    The specific heats of Armco iron which was cold compressed with a high-speed working velocity (about 4.3m/s) and a low-speed one, were measured by Sykes' method, and stored energies were calculated and compared with each other. The results were as follows:
    (1) The stored energy was released in two steps.
    (2) The ratio of stored energy to the working energy were 4.9% in the case of the high-speed working velocity and 9.4% in the case of the low-speed working velocity.
    (3) The stored energies increased proportionaly to log (ho/h). Here ho is the height of uncompressed samples, h is the height of samples after compression.
    (4) The authors can not clear the difference of the stored energies between the case of high-speed compression and low-speed one within the accuracy of this experiment. Lastly, they discussed the results using Mott and Stroh's theory.
  • THERMODYNAMIC INVESTIGATION OF NON-METALLIC INCLUSIONS IN STEEL (II)

    pp. 31-38

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    When titanium (zirconium or vanadium), nitrogen and carbon are contained in steel, nitride and (or) carbide of the element are formed according to the degree of stability of these compounds. The free energy equations of the formation of nitrides and carbides in steel are derived by the same method described in the previous report (Tetsu to Hagane (1955) vol. 41, No. 10, p. 1082). The equilibrium relations of the formation of titanium-, zirconium- and vanadium-nitrides and carbides are calculated by these equations in several cases of different contents of these elements. According to the results of calculation, both titanium-(zirconium-) nitride and carbide are estimated to be effective as grain growth inhibitors, but inclusions which are precipitated in austenite may be considered to be more effective as inhibitors than those in molten steel. Vanadium nitride may also be effective as the inhibitor but there remains some uncertainty. Vanadium carbide 'VC' does not precipitate in steel while 'V4C3' may precipitate in austenite and may be effective as the inhibitor.
  • STUDIES ON BALL BEARING STEELS (V)

    pp. 39-43

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    In this report the behavior of spherical carbide going into solution in austenite was studied quantitatively, and the behavior of hardness and fracture roughness in austenite was studied together with.
    The results obtained are summarized as follows;
    1) At each heating temperature, the hardness increases with the holding time. At 840°C temperature, the hardness increases rapidly and is saturated after 1 hour, and at 860°C temperature it is considerably high in mere 5 minutes of the holding time.
    2) Between SKF and Japan-made ball bearing tubes the behaviour of the carbide in austenite is very different. The carbide solution of the former is saturated in 50-60 minutes, and one of the latter in 30-50 minutes at each heating temperature. In the former the intervals of saturated carbide contents at each heating temperature are equal, but not equal in the latter. Namely, in the latter the intervals of saturated carbide contents between 780-800°C and 840-860°C temperature are considerably wide, and these between 800°C, 820°C and 840°C temperature are narrow.
    3) The fracture roughness don't always agree with the visual observations, and it is considered generally that the fracture roughness increases. at the point from the sliding failure to the separate one.
  • STUDIES ON ANISOTROPIC MK PERMANENT MAGNET (III)

    pp. 43-47

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    The magnetic properties of the anisotropic MK permanent magnet are the most excellent in commercial magnets. Its applications to industrial field are now expanding. In this report, magnetic properties, magnetic agings and industrial applications of this permanent magnet were investigated.
    The magnetic properties of this magnet are listed in Table 1.
    Effects of various demagnetizing factors on the magnetic stability were examined. The ratio of remanent induction decreased was in proportion to logarithm of numbers subjected to repeated demagnetization, such as alternative field, mechanical shock and attraction of iron. As for the efficient use of magnet materials, the method of design in a static circuit was illustrated numericaly. Determination of leakage factors was difficult. The leakage flux depends on the reluctance of air gap in similar circuit. As the representative example of industrial uses, mention was made on permanent magnets for speaker and magnetron.
  • STUDIES ON CEMENTITE CRACKS OF HIGH CARBON STEEL (II)

    pp. 48-54

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    The effects of the addition of hydrogen to 1.4% C file steel; 1.0% C, 1.4% Cr bearing steel; 1.0% C, Cr-W tool steel are investigated. Samples are taken from the outer side of the billets which have been confirmed that any "Acm cementite cracks" were not existed.
    The followings are conclusions.
    (1) "Acm cementite cracks" are generated in hyper-eutectoid steels by the addition of hydrogen, and the fact has been proved that the main cause of the formation of "Acm cementite cracks" was the existence of super-saturated hydrogen in the steel.
    (2) It has also been proved that so-called macro hair-cracks and flakes on fractured surface were only another apperances of "Acm cementite cracks"
    (3) The characteristic features of flakes occurence on hyper-eutectoid steel, which have not been able to explain by the use of theories about the flakes occurence on hypoeutectoid steel, can easily be understood by considering the existence of "Acm cementite cracks.
  • STUDIES ON THE GAS CARBURIZATION

    pp. 54-61

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    Such parts as gas converting retort, heating retort, muffle, basket, fixture, net, conveyer, fan, fan shaft, etc. made of heat resisting steel and also metallic heat elements or radiant tube usually are used to controlled atmospheres furnace for gas carburizing, bright heating or gas carbonitrizing.
    These parts are eroded at high temperature due to oxidizing, carburizing, nitriding or carboniriding.
    In this paper are reported such erosions observed as for many materials treated in controlled atmospheres. As the results these materials are classified to four types of erosion, A, B, a and b.
  • ON THE DETERIORATION OF QUENCHING OILS (III)

    pp. 61-66

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    The effect of several kinds of inhibitors against the deterioration of quenching oils was examined experimentally. It is concluded, from the results, that most of oxidation inhibitors examined here seem to elongate the initial stage (induction, period) of deterioration and to accelerate the oxidation of oil in the later stage (polymerizing period) by a catalytic action of the oxidation products of inhibitors. Although for quenching oil the inhibitor should be effective not only in the initial stage but also in the later stage of oxidation process, there was a difficulty in finding such inhibitor. But, some good effects were observed in certain cases, that is, n-phenyl-α-naphthyl-amine in soya-bean oil, di-phenyl-amine and di-tert.-buthyl-para-cresol in 110-dynamo oil and di-tert. -buthyl-para-cresol in 120-cylinder oil, when the concentration was about 0.5%.
  • RECENT DEVELOPMENTS IN WIRE ROPE

    pp. 67-76

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  • 鉄鋼生産技術の展望

    pp. 77-80

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  • 抄録

    pp. 81-85

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  • 鉄鋼ニューズ

    pp. 86-91

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  • 国内国外刊行誌参考記事目次

    pp. 87-91

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  • 統計

    pp. 94-96

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