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

Tetsu-to-Hagané Vol. 62 (1976), No. 13

  • 大型鋼塊の製造と加工特集号刊行に際して

    pp. 1603-1604

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    Readers Who Read This Article Also Read

    1. Effect of Rolling Practices on Annihilation Process of Micro-Porosity in Big Ingot Tetsu-to-Hagané Vol.62(1976), No.13
  • Manufacturing of Large Rimmed Ingot

    pp. 1605-1616

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  • Manufacturing of Large Ingot for Pipe

    pp. 1617-1628

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  • Sound Surface Quality of Large Capped Steel Ingot

    pp. 1629-1640

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    To decrease skin blowholes and get a sound surface quality, the effects of deoxidation degree and chromium addition on the size and distribution of blowholes in the rim zone were studied.
    The results obtained are as follows;
    1. The thickness of solid skin and the distribution of blowholes in the rim zone are greatly influenced by the balance of carbon, manganese, and oxygen in liquid steel.
    2. It is believed that the thickness of solid skin is required at least 17mm to prevent seamy defects of slab. The next relation is obtained as the condition of deoxidation to keep the thickness of solid skin larger than 17mm.
    [C]·[O]-0.56 [Mn]≥0.0182 υ-5, 135 Where, [C], [O], [Mn]: content in liguid steel (10-2%)υ: teeming rate (mm/min)
    3. Chromium addition is effective to decrease the number and size of blowholes in the rim zone. It is considered that this phenomenon is based on the decreasing of surface tention by chromium addition.
  • On the Solidification and Segregation of the Large Killed Steel Ingots

    pp. 1641-1652

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    Segregation in steel ingots cause the degradation of mechanical and chemical properties. We have experimented on segregation and solidification of the large steel ingots (24-39T) and obtained the results as follows:
    1. The solidification pattern in the large flat steel ingots is proportional to the square root of timeafter teeming in the first stage solidification and the square of it with the formation of sedimental crystals.
    2. By scraping the liquid steel in a mold, the inverse V segregation disappears in the near surface of ingot top, but it remains in the ingot bottom. Further, the inverse V segregation lines become thin and shift to the inner parts of the ingot and the floating velocity of the rich liquid steel quickly increases.
    3. The formation of the inverse V segregation is closely related with the solidification velocity and the critical solidification velocity of the formation of the inverse V segregation becomes small byscraping the liquid steel in a mold.
    4. By R. E. M. addition to the liquid steel in a ladle, the inverse V segregation lines in sulfurprint become the white segregation and also the large inclusion is insignificant. Judging from these results, we could confirm the effectiveness of the method of R. E. M. addition to the liquid steel in a mold (BCCTMethod).
  • Mechanism and Removal of the Accumulation in the Sedimental Zone of Inclusions Precipitating during Solidification of Large Ingots

    pp. 1653-1667

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    The solidification structure, solute segregation, constitution and distribution of inclusions in rare earth (RE) treated large ingots have been investigated. A concentration region, called “The Rare Earth Zone” which is bound by [%RE][%S] =2.7-8.0 and [%RE][%S]<=15×10-5 on RE vs. S coordinates, has been found to give a satisfactory sulphide shape control without causing any harmful accumulation of RE-sulphides and RE-oxysulphides in the sedimental zone of the ingots. A theoretical model has been given to successfully account for the sedimental zone accumulation, anomalous A-segregation, and the reversion, named “S-Reversal”, of the segregation pattern in the RE-treated ingots. The constitution and origin of inclusions typical in the RE-treated ingots have also been interpreted in terms of the model supplemented by thermodynamic considerations.
  • Effects of Ingot Weight and Size on Loose Structure and the Reduction of Area in Z-direction of Steel Plate

    pp. 1668-1679

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    Recent tendency to the enlargement of various structures made of steel plates, such as ships and bridges brings about the need for the production of the large ingots which weigh more than 30 tons. Such large ingots have a loose structure in the center of ingot along axis, which deteriorates not only the homol.eneity of solidification structure, but also mechanical properties of end-products, eapecially reduction of area in tensile test in the thickness direction of plates (Z-tensile test).
    Research works on the loose structure and its effects on mechanical properties have been seldom reported before. The present report has proposed a new method using ultrasonic test to measure quantitatively the looseness of the structure of ingots. With this method, the effects of ingot weight and shape on the formation of the loose structure were investigated and clarified. Furthermore, the change of the looseness by rolling was investigated. Investigations have revealed that the reduction of area in Z-tensile test, which is of prime importance on heavy plates, is substantially dependent on the looseness of the plates originating from that of ingots.
  • Production of Large Steel Ingots for Wire Rod and Bar

    pp. 1680-1690

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    This paper deals with the production of large steel ingots for wire rod and bar. Lately steelmakers attempt to produce larger ingot for productivity, but in this case it is most important to reduce the segregation.
    The qualitative problems caused by the segregation are well known as follows;
    (1) Fluctuation of mechanical properties.
    (2) The troubles at the secondary processing such as the fracture during drawing and cold heading.
    (3) The fluctuation of machinability, etc.
    The segregation in 3t, 5t, 7t and 10t killed ingots was investigated and the effect of ingot size on the segregation is considerably made clear.
    As the representative procedure to reduce the segregation, the optimization of head volume and top discard ratio, the ingot-case designing and the holding time after the pouring are considered.
  • Operation of Arc Heating Furnace on Manufacturing Gigantic Ingots and Segregation of Gigantic Ingots

    pp. 1691-1697

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    The techniques and procedure for manufacturing gigantic ingots heavier than 200 t are described. Especially, practical results of an arc heating furnace which plays an important role in the procedure and segregation of gigantic ingots are discussed in detail. By appropriate operations of the arc heating furnace, hydrogen and phosphorus are kept unchanged, and oxygen and sulphur decrease to very low levels. Furthermore, the temperature can be accurately controlled. The application of multipour technique reduces segregation and its degree is dependent on kinds of steel. V-segregation and inverted V-segregation in steel deoxidized with carbon in vacuum seem to be very slight.
  • Quality of the Large ESR Ingots and Products from Them

    pp. 1698-1707

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    In order to evaluate the metallurgical homogeneity of large ESR ingots, longitudinal cross sections of the 1 500 mm∅ remelted ingots were examined by metallurgical method, and also the influence of the ESR melting rate was investigated. Furthermore, to confirm the quality of the ESR ingots, some experiments in the application of ESR process of turbine parts were carried out.
    The results are as follows:
    (1) Freckles and equiaxial crystal are observed at the top portion of a 1500mm∅ ESR ingot with 2000kg/hr melting rate. The defects are reduced by decreasing the melting rate.
    (2) It is suggested that the formation of freckles may be related to distance between solidus and liquidus lines.
    (3) From the attempt of manufacturing the turbine parts by the ESR process, superior characteristic of homogeneity and mechanical properties are obtained.
  • Rolling and Heat Treatments of Heavy Section Low Alloy Steel Plates

    pp. 1708-1719

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    he heavy section low alloy steel plates are used for pressure vessels for nuclear reactor, desulfurizer of crude oil and so on. The integrity in quality, therefore, is required for those plates.
    The factor affection the internal soundness and notch toughness of heavy section low alloy steel plates are discussed in relation to the rolling process from ingot to plate and the heat treatment after rolling.
    Theoretical analysis concerning constrained yield stress in rolling direction was applied for the rolling of extremely thick plate and it is concluded that adapting high “shape factor”, that is, high reduction in the stage of final pass in the rolling process is effective to reduce internal defects in plates.
    Precipitation behavior of aluminum nitride in A553B steel plate during heat treatment after rolling is discussed in relation to the austenite grain size and notch toughness of plate after final rolling, and cooling down to 400°C before normalizing is recommended for obtaining good notch toughness.
    Selection of temperature and time for dehydrogenation at ferrite region is discussed and it is shown that the optimum temperature for dehydrogenation must be determined by taking the microsegregation in the plate into consideration.
  • Effect of Rolling Practices on Annihilation Process of Micro-Porosity in Big Ingot

    pp. 1720-1733

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    The effect of rolling conditions on the process of the annihilation of the micro-porosities in the big ingot was investigated to clarify the possibility to get the sound ultra-heavy plate only by rolling, eliminating pre-forging process.
    It was deduced from the results of the experiments that the most important factor for the annihilation of the micro-porosities at the center of the thickness was the compressive stress perpendicular to the rolling plane at the center of the thickness. It was clearly demonstrated that the micro-porosities were easily annihilated in the early stage of rolling under such rolling conditions that enabled the compressive stress to exceed the resistance to deformation significantly. These conditions were realized by the rolling process with the large amount of reduction per rolling pass (“heavy reduction-rolling”) utilizing the work roll with large diameter, while in the case of light reduction-rolling the micro-porosities retained as theelongated imperfections up to the late stage of rolling. It was also confirmed that both slow rolling speed and high rolling temperature assisted the annihilation of thin elongated micro-imperfections. This phenomenon can be interpreted in terms of the effect of time and temperature on the annihilation of interfaces by means of diffusion and viscous flow processes. It was concluded that it should be possible to manufacture the sound ultra-heavy plates without pre-forging process, provided that the combination of aforementioned considerations were taken into account for the rolling process.
    x

    Readers Who Read This Article Also Read

    1. 防振鋼板・冷延鋼板・再結晶・介在物・被削性・マルエージ鋼 Tetsu-to-Hagané Vol.62(1976), No.11
    2. The Effect of K2O, Na2O and CaO Addition to Fe2O3 Single Crystal on Its Reduction Tetsu-to-Hagané Vol.62(1976), No.12
    3. 大型鋼塊の製造と加工特集号刊行に際して Tetsu-to-Hagané Vol.62(1976), No.13
  • On the Heat Treatment and Properties of Large Shaft Forgings

    pp. 1734-1743

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    The demands of size and quality of large steel shaft forgings for ship building, power plant, steel plant, etc. are rapidly increasing, and some of these products are manufactured from ingot weighing more than 300 tons. According to the increase of ingot size, micro- and macrosegregation and also mass effect of the product increase. Thus, special care should be paid to the heat treatment of such large shaft forgings.
    In this report, the fundamental matters of heat treatment of large shaft forgings are briefly described, and some mechanical test results, internal properties of products, residual stresses are also discussed.
  • The Heat Treatment and Mechanical Properties of Heavy Gauge Steel Forgings and Plates

    pp. 1744-1755

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    Development of larger quality steel plates, castings and forgings is one of the key points in the recent spectacular growth of technical advancement in a vast range of industries such as heavy electric machinery, nuclear power generation, shipbuilding, steel making and chemicals.
    This report discusses important problems related to heat treatment for heavy gauge products, such as (1) hydrogen-induced cracking, (2) grain size, (3) residual stress and (4) temper embrittlement. Then, metallurgical factors in heat treatment influencing on the mechanical properties and investigation results of actual products are described concerning heavy section plates and forgings for nuclear use.
  • Theoretical Study of the Deformation of Quenched Steel Bar

    pp. 1756-1766

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    The deformation of quenched steel bar was theoretically studied by the finite element method. The findings are as follows:
    1) In the austenite steel, a convex type plastic deformation proceeds owing to shrinking of the case in the initial stage of the cooling where the temperature difference between the case and the core of the bar increases. As the cooling proceeds and the temperature difference decreases, a concave type plastic deformation proceeds, cancelling the convex, owing to the shrinking of the core. As the latter concave does not fully cancell the convex, some convex type deformation remains at room temperature.
    2) Transformation to martensite and/or bainite enhance the concave type deformation of the latter stage because of their higher rigidity. Therefore, the concave type deformation results when the bar was water-quenched and the steel transformed into the low temperature products.
    3) When the bar was quenched in oil the martensite transformation has less effect on the concave type deformation than in the case of water-quenching, because of smaller temperature defference at low temperature range.
    The deformations obtained by theoretical and experimental study were in reasonable agreement.
  • 抄録

    pp. 1767-1772

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