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

Tetsu-to-Hagané Vol. 69 (1983), No. 14

  • Effects of Stress on Phase Transformations and Precipitations

    pp. 1531-1539

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  • Effect of Neutron Irradiation on Mechanical Properties of Austenitic Stainless Steels

    pp. 1540-1548

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  • Development of Remaining Service Life Prediction System for High-temperature Plant Components

    pp. 1549-1555

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  • Application of Solvent Extraction in Iron and Steel Making Industry

    pp. 1556-1566

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  • Characterization and Control of Steel Surfaces

    pp. 1567-1577

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  • Improvement of Oilless Blast Furnace Operation by Applying Size-segregated Sinter Charging

    pp. 1578-1584

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    A charging method of sinter segregated into fine and coarse particles was developed, in order to improve the gas flow distribution in a blast furnace under all coke operation. In advance, the characteristics of the distribution of size-segregated sinter at the furnace top was investigated by model tests. The main results obtained are as follows:
    (1) The average value of void fraction of sinter separated into fine and coarse particles is higher by 1 to 2% than that of conventional unseparated sinter.
    (2) Since the angle of inclination of fine sinter is considerably influenced by gas flow, fine sinter should be charged in the peripheral region of the furnace where the gas velocity is low.
    (3) Desirable charging mode is the type of L↓(S)↓ because this mode guarantees good gas permeability and stable burden profile.
    (4) The thickness of layer which contains the fine sinter layer in the peripheral region should be decreased in order to develop the peripheral gas flow and flatten the radial gas flow distribution.
    The charging method was applied to Muroran No. 4 BF without oil injection and proved to be effective for a reduction of coke rate and an improvement of gas permeability. As the result of the measurements by a vertical probe in the furnace, the cohesive zone profile was estimated to be an inverted V type with a low apex and a high root.
  • Refining of Hot Metal with Soda Ash in Trough-type Continuous Refining Furnace and Fluid Flow Characteristics of Hot Metal and Slag in the Furnace

    pp. 1585-1590

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    The multi-stage steelmaking process with soda ash (Na2CO3) was proposed. Dephosphorization and desulphurization of hot metal, the most important unit processes in the process, were studied. Experiments on the continuous refining of hot metal with Na2CO3 were carried out using the trough-type continuous refining furnace. The furnace was divided in two chambers and the first (upper stream) chamber was provided for desiliconization with oxygen and iron are and the second one was for dephosphorization and desulphurization with Na2CO3. In the second chamber the hot metal and slag flowed in counter currents.
    The furnace was able to process the hot metal at a rate of 45 t/h and the refined hot metal was transported to the steelmaking shop. The operation for 120 hours in campaigns proved the stability in reaction temperature and low wear rate of the refractory in the refining section. By analysing the tracer concentration in the exit stream with the mixed model, Peclet numbers for the hot metal and the slag flows were estimated as 6.7 and 2.0 respectively.
  • Dephosphorization of Liquid Iron by the Slag of Na2O-SiO2 System

    pp. 1591-1598

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    As one of fundamental research on the refining of molten iron by sodium carbonate, the experiments were made of the dephosphorization of liquid iron by the flux added Fe2O3 or sodium carbonate (Na2CO3) to sodium silicate having various ratio of Na2O and SiO2 at temperature of 1 550, 1 600, and 1 650°C.
    The results of these experiments indicated clearly the effects of addition of Fe2O3, slag basicity, temperature, and initial phosphorus content in liquid iron on the dephosphorization by the slag of Na2O-SiO2 system, and investigation also showed the refining actions of Na2CO3 in the slag.
    Furthermore, a discussion was made on the equilibrium relationship of dephosphorization reaction by the slag of Na2O-SiO2 system, and a following expression was obtained;
    2P + 5(FeO) = (P2O5) + 5Fe log kp = log (%P2O5)/[%P]2(%T.FeO)5=8.67 log(%Na2O)-14.55(1 600°C)
    From the comparison of this expression with that of the slag of CaO system reported previously, it became clear that the dephosphorization by the slag of Na2O system is more effective than by that of CaO system.
  • Analysis of Blowhole Formation and Suppression during Solidification by Cold Model

    pp. 1599-1606

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    CO blowhole formation on the surface of the continuously cast slab is one of the most important problems in continuous casting of slightly deoxidized steel, such as pseudo-rimmed steel.
    Model experiment with aerated water was carried out in order to understand the mechanism of CO blowhole formation and suppression with molten flow during solidification of steel.
    The results obtained are summarized as follows.
    1) Equilibrium distribution constant of CO2 is estimated to evaluate the CO2 blowhole formation and suppression quantitatively.
    2) The shape of CO2 blowholes chiefly depends on the concentration of CO2 at the solidification front and the solidification rate.
    3) CO2 blowholes are suppressed completely with fluid flow at the certain velosity which is related to CO2 content of aerated water.
    4) The models of blowhole formation and suppression based of the experimental results are proposed. The calculated results agree well with the measured value.
  • CO Blowhole Formation and Suppression in Continuously Cast Slab

    pp. 1607-1614

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    The key factor in continuous casting of rimmed or semi-killed steels is the suppression of CO blowholes on the slab surface.
    This report deals with the critical condition of blowhole formation in slabs cast by the bow type machine and the suppression of blowholes.
    (1) The critical free oxygen concentration for blowhole formation for hot rolled plate grade of C greater than or equal;0.08% is approximately 55 ppm whereas that for cold rolled sheet of Cless than or equal0.06% increases with decreases in C concentration.
    (2) Blowholes can be successfully suppressed by causing the molten steel to flow at the vicinity of meniscus at the required flow corresponding to the composition of steel.
    (3) The critical values of enriched solute elements and the partial pressure of CO, PCO at the solid-liquid interface of solidifying steel for blowhole formation are estimated by introducing the mutual reaction model in the multiple components system. The shapes of blowholes estimated from the model agree well with the measured ones.
  • Continuous Casting of Pseudo-Rimmed Steel with Electromagnetic Stirring in the Mold

    pp. 1615-1622

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    Realization of the continuous casting of undeoxidized steel is one of the most important tasks in continuous casting technology.
    This report describes the development of production of the pseudo-rimmed steel with the electromagnetic stirrer installed in the mold.
    (1) To produce a good slab free from CO blowholes in the subsurface layer, it is necessary to make the factors suitable, such as the position of the linear moters, stirring conditions and the shape of mold.
    (2) Pseudo-rimmed steel of sol. Al[less thsn or equal]0.004%, which is equivalent to rimmed or capped steel, can be continuously cast by electromagnetic stirring the molten steel in the mold.
    (3) The movement of the molten steel also has beneficial effects on the slab quality, such as uniformalization of shell thickness and reduction of inclusions near the subsurface layer.
  • Reduction of Residual Stress in Rolled H-beam

    pp. 1623-1629

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    In a hot-rolled H-beam, covering the upper surface of web by insulator (web-insulating) and cooling the outside surface of flange by water (flange-cooling by water) after rolling are considered effective measures for reducing the residual stress. To confirm this, the relation between the residual stress and the time of their treatment under various finishing temperature conditions was investigated using the analytical method for thermal stress. This method is characterized by taking phase transformation into consideration.
    The outline of results obtained is as follows;
    (1) The longer the time to insulate web or to cool flange after rolling is and the smaller the difference in finishing temperature between flange and web is, the lower the tensile residual stress in flange and the compressive residual stress in web are. Namely the residual stress is reduced in the whole cross section in this case.
    (2) In the case of large size H-beam (H : 900×300×16×28 mm), the time to cool flange (heat transfer coefficient : 250 kcal/m2·h·°C) after rolling for reducing the residual stress in web is about a quarter of the time to insulate web.
    (3) It is possible to reduce the residual stress below the required value by combining the control of the difference in finishing temperature with the control of the difference in cooling rate between flange and web after rolling.
    (4) The choice of either web-insulating or flange-cooling by water after rolling should be made by considering the influence on the metallurgical quality and the ease of control as well as the effect of reducing residual stress.
  • Effect of Cathodic Protection Conditions on the Stress Corrosion Cracking of Line Pipe Steels

    pp. 1630-1637

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    Stress corrosion cracking (SCC) of buried line pipe steel was studied from practical aspects of view including cathodic protection conditions. The results obtained are summarized as follows:
    1) The most probable occurrence of SCC on buried steel pipelines was thought to be limited to the sites of cathodic disbonding accompanied by corrosion rusts.
    2) Cathodic protection current of not less than 1 mA/cm2 could cause cathodic disbonding of protective coating on a steel pipe, and could form a sufficient concentration of alkali to produce carbonate-bicarbonate SCC.
    3) The more predominant environment to produce SCC on a buried line pipe steel was thought not a caustic alkali solution but a carbonate-bicarbonate solution because of a high partial pressure of CO2 in the soil.
    4) Those pipelines which were cathodically protected at the polarization potential between-1 000 and-1 350 mV vs. Cu-CuSO4 and at the cathodic current density of less than 1 mA/cm2 were thought free from SCC.
  • Characteristics of an Oxidation Inhibitor Composed of Refractory Powder-SiO2-MnO2-Colloidal Silica-Coking Bond

    pp. 1638-1644

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    Characteristics of a newly developed oxidation inhibitor composed of a refractory powder-SiO2-MnO2-collodial silica-coking bond have been investigated.
    The steel coated with the inhibitor shows an excellent antioxidability as compared with non-coated steel at high temperatures from about 1 000 to 1 250°C.
    The inhibitor can be easily applied to the surface of ordinary steel slab by spraying in production line.
    The production test also shows that the inhibitor film on the heated slab can be removed completely by subsequent scale breaker and that the steel sheets after hot rolling have a surface without defects.
    In addition, a high degree of production yield of the rolled sheets has been obtained because of the minimum scale loss.
    Antioxidation effect of the inhibitor has been found to depend on the formation of eutectic material that effectively reduces the oxygen diffusion from atmosphere.
  • Characteristics of an Oxidation Inhibitor Composed of a Refractory Powder-SiO2-Al-Synthetic Mica-Colloidal Silica-Coking Bond

    pp. 1645-1651

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    Characteristics of a newly developed oxidation inhibitor composed of a refractory powder-SiO2-Al-synthetic mica-colloidal sillica-coking bond have been investigated.
    The steel coated with the inhibitor shows an excellent antioxidability as compared with non-coated steel at high temperatures from about 1 000 to 1 300°C. The inhibitor can prevent intergranuar oxidation and selective oxidation of alloying elements. The inhibitor can be easily applied to the surface of slab by spraying in production line.
    The production test also shows that the inhibitor film on the heated slab can be removed completely by the subsequent scale breaker and that the steel sheets after hot rolling have a surface without defects. In addition, a high degree of production yield of the rolled sheets has been obtained because of the minimum scale loss.
  • Effect of Sulfide Former Elements on the Hot Ductility of High Ni-Cr Steels and Ni-base Alloys

    pp. 1652-1659

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    A study was made to search the beneficial elements and the quantity to be added, in order to improve the hot ductility of high Ni-Cr steels and Ni-base alloys by addition of sulfide former elements. It was found that good ductility was obtained by addition of elements having much larger atomic radius than Ni, and their amounts were required to be sufficient for sulfide formation but not to be excess. Namely, it was necessary to fix sulfur in the alloys as ZrS, MgS etc. and not to form metallic compounds having low melting point
    x

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    1. Creep Rupture Properties and Creep Fracture Mechanism Maps for Type 304 Stainless Steel Tetsu-to-Hagané Vol.69(1983), No.14
  • High Temperature Corrosion of Mild Steel, 16%Cr Steel, Nickel and Ni-20%Cr Alloy in the Presence of Calcium Sulfate and Carbon

    pp. 1660-1667

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    Ash deposits, especially alkali and alkaline earth sulfates, have been said to be an important source of the hot corrosion of valves and pre-combustion chambers in automobile diesel engines.
    In the present work, to clarify the corrosion behavior, crusible-type corrosion tests by CaSO4-C mixtures have been carried out on pure nickel, iron and their Cr-containing alloys in the temperature range from 650°to 1 100°C for 4 h in air.
    The results obtained from gravimetric measurements and metallographic examination are summarized as follows :
    1) The CaSO4 alone is not corrosive for above metals and alloys, however the addition of C causes very severe attack, especially on Ni-20% Cr alloy.
    2) On Ni and Ni-20% Cr alloy the temperature dependence of the corrosion caused by CaSO4-20% C mixture is different from that of well-known SO2 gas corrosion; nickel shows a monotonic increase in weight loss with temperature and Ni-20% Cr alloy shows a maximum at about 875°C.
    3) In the corrosion scale, the sulfides and the oxides of each element in alloys are recognized; this scale morphology is characteristic of the sulfidation-accelerated oxidation.
  • Creep Rupture Properties and Creep Fracture Mechanism Maps for Type 304 Stainless Steel

    pp. 1668-1675

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    Specimens of Type 304 stainless steel ruptured at temperatures between 600°and 800°C and with rupture periods up to about ten years have been examined metallographically in order to deduce creep fracture mechanisms and make creep fracture mechanism maps.
    The steel has showed four different creep fracture mechanisms: transgranular creep fracture, wedge-type cracking at triple point, intergranular cavitation, and cracking at sigma/austenite interface. The rupture strength in the fracture field of the cracking at sigma/austenite interface shows marked decrease with increasing time to rupture. Stress index of time to rupture and apparent activation energy for rupture in this fracture field are in the ranges of 1.4-2.0 and 160-170 kJ/mol, respectively, suggesting that the rupture life in this field is controlled mainly by means of grain boundary diffusion growth of the cracks. Metallographic observations indicate that relatively high aluminum content (about 0.05 wt%) may be responsible for early formation of the grain boundary cracks due to precipitation of AIN associated with the grain boundary sigma phase.
    x

    Readers Who Read This Article Also Read

    1. Effect of Sulfide Former Elements on the Hot Ductility of High Ni-Cr Steels and Ni-base Alloys Tetsu-to-Hagané Vol.69(1983), No.14
  • The Effect of Cooling Rate from Austenitizing Temperature on the Microstructure and Toughness of the 0.35C-3Cr-3Mo-V Hot Work Alloy Tool Steel

    pp. 1676-1683

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    The effect of quenching rate from austenitizing temperature on the microstructure and toughness of a 0.35C-3Cr-3Mo-V hot work alloy tool steel was investigated.
    (1) Plane strain fracture toughness and charpy impact value are reduced abruptly as the quenching rate decreases from the rate by oil quenching to the rate of the half temperature time of 35 min, and gradually reduced as the rate further decreases.
    (2) The microstructural changes corresponding to the above behavior of toughness can be summarized as follows:
    (a) Formation of upper bainite and increasing of its volume ratio to martensite. (b) Increasing of width of bainite grain, compared with that of martensite lath, and strong tendency to the chain like carbide distribution and agglomeration of carbide particle precipitating along bainite grain boundaries compared with carbide precipitating along martensite lath boundaries. (c) Increasing of the effective grain size. (d) Preffered precipitation of carbide along the grain boundaries of prior austenite. (e) Increasing of distribution density of extremely fine carbide precipitates. (f) Transition of bainite configuration from lath to granular type and further increased volume of carbide precipitated along the grain boundaries of prior austenite, and further increased distribution density of extremely fine cardide precipitates. (Half temperature time 520 min)
    (3) Fatigue crack propagation rate are somewhat increased by the formation of upper bainite. This corresponds to the increase of distribution density of extremely fine carbide which precipitates during tempering of upper bainite.
  • Approaches to the Continuous Refining Processes

    pp. 1684-1689

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  • 日本における工学教育および工業教育のあり方

    pp. 1690-1692

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  • 抄録

    pp. 1693-1695

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  • 状態図の研究

    pp. 1696-1696

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