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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 70 (1984), No. 15

  • Future Problems on Recrystallization and Texture of Steel Sheets

    pp. 1795-1800

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  • Recent Development in the Research Technique on Recrystallization

    pp. 1801-1807

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  • 研究と予算/再結晶集合組織に関する用語の不統一について/ミラー指数/結晶粒の自動測定法雑感/「Recrystallization Processing」/粒径について/結晶粒界は宝の山/岩石の再結晶/集合組織の功罪

    pp. 1807-1807,1818

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  • Deformation Structures as Nucleation Sites for Recrystallization

    pp. 1808-1815

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  • Critical Review on the Recrystallization in situ

    pp. 1816-1818

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  • Grain Boundary Structure and Its Mobility

    pp. 1819-1827

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  • Crystallization of Amorphous Alloys

    pp. 1828-1832

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  • Effect of Heat Treatment Prior to Cold Rolling on the Recrystallization Texture in Iron-Carbon Single Crystals

    pp. 1833-1840

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    For the purpose of investigating the formation mechanism of recrystallization texture, the effects of carbon and its existing state on cold rolled and recrystallization texture were studied in iron-0.02% carbon single crystals.
    The results obtained are described as follows.
    In crystals with the initial orientation of (001) [110], fine carbides markedly retarded the recrystallization.
    In crystals with the initial orientation of (110) [001], the cold rolled textures are {111} <112> and the recrystallization textures are {110} <001> irrespective of the variation in the existing state of carbon.
    In crystals with the initial orientation of (111) [110], cold rolled textures are retained in the initial orientation, and recrystallization textures are composed of two orientations {111} and near {110}. The near {110} recrystallization texture was formed by the preferential recrystallization at the region of {112} <111> slip system operated during cold rolling. Solute carbon increased the {110} recrystallization texture and fine carbide suppressed the recrystallization of {100} grains.
    The formation mechanism of recrystallization textures in low carbon steels was discussed, based on the obtained results.
  • Rolling and Recrystallization Textures in Single Crystal of Al-0.03%Fe Alloy Rolled to (123) [412] Orientation

    pp. 1841-1848

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    Formation of recrystallization nuclei was investigated by means of X-ray diffraction and electron microscopy, using aluminum single crystal whose orientation is one of the stable orientation during rolling. Rolling texture is almost the same as the initial orientation but accompanied with orientation spread around [111] axis normal of cross slip plane of active slip system. On annealing, growth of subgrains with the same orientation as that of the tail of orientation spread were observed by electron microscopy. Recrystallization textures at 623 and 723 K have an orientation relationship which is described by 48° rotation around [111] axis. Since the other components derived by orientation relationship of preferential growth were not observed, it was suggested that the elongated cells with the same orientation as that of recrystallization texture were effective as the site of recrystallization nuclei.
    Recrystallization texture at 673 K was ascribed to continuous recrystallization resulting from competition of precipitation and recrystallization.
  • Recrystallization Behaviour of Shear Band in a Cold-rolled Copper Single Crystal

    pp. 1849-1856

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    The recrystallization behaviour of shear bands induced in a cold-rolled (112) [111] copper single crystal was investigated. The orientations of small recrystallized grains were determined by means of the electron chanelling pattern (ECP) and the Kossel pattern technique.
    At the early stage, recrystallization occured only within shear bands, however, the recrystallized grains did not grow into the matrix regions between shear bands. Most of grains grown in a shear band had the twin relationships of the first to the third order each other. At the later stage, recrystallization in the matrix region occured and the preferential growth of the grains having a 30° <111>relationship with the matrix texture was observed. These recrystallization behaviours can be expressed by assuming that the texture in well-developed shear bands is different from that in the matrix region.
  • Unidirectional Recrystallization in Cold-swaged Ni Alloys

    pp. 1857-1863

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    Unidirectional recrystallization in cold-swaged Ni alloys was investigated at temperature gradients of 900, 450 and 140 K/cm, and the effects of temperature gradient, transfer rate and solute atoms on recrystallized structures were studied. Though highly elongated grain structures were observed in Ni-Cu alloys above 1 at% Cu at a temperature gradient of 900 K/cm, higher temperature gradients were needed for alloys of lower Cu concentration. The temperature gradient needed for unidirectional grain growth, the maximum transfer rate and the grain size decreased with increasing solute concentration. The kind of solute atom was another important factor and much influenced the recrystallized structures. As quenched interfaces reveals the feature of recrystallization processes, the unidirectional recrystallization technique is expected to be useful for study of recrystallization.
  • Morphological Analysis for Primary Recrystallized Grain Structures of Pure Iron by a Nucleation and Growth Model

    pp. 1864-1869

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    The morphological analysis of recrystallized grain structures of pure iron was carried out to make clear the relation between the structure and recrystallized condition. Specimens were prepared by cold rolling to the reductions of 60% and 80% and annealing at 650°C or 750°C for 10-240 min. Photographs of the microstructures in the longitudinal cross section parallel to the rolling direction were taken and grain boundaries were traced on paper for image processing. Average morphological characteristic values of 4πA/P2, LD/BR, CP/P were calculated for each grain structure, where A, P, LD, BR and CP represent the grain area, perimeter, the longest dimension, the narrowest breadth and convex perimeter, respectively. Coefficients of variation for the distributions of grain area were 1.0-1.3 and those for the distributions of grain size were 0.54-0.60. From the average values of 4πA/P2 and CP/P, it was shown that each grain in the structures for the 80% rolled specimens showed more stable shape than that for the 60% rolled specimens. Compared with the structures obtained by computer simulation study, the recrystallized grain shapes had anisotropy generated by the ellipsoidal growth with the axial ratio of 2.0 and the growth rate directed to the major axis of 0.2(unit length/unit time) at the nucleation rate of 100 (number/unit area·unit time). It was estimated that the anisotropy resulted from the anisotropic shape of nucleus.
  • Effect of Grain Size on the Strength of Ll2 Intermetallic Compounds

    pp. 1870-1877

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    Temperature dependence of strength in Ni3Al and Ni3Si with various grain sizes, 4 to 275 μm, are investigated through compression tests. The finer the grain size is, the positive temperature dependence of strength appears to be weaker. Thus HALL-PETCH parameter, ky, for both alloys is evaluated at various test temperatures and is found to decrease above 200 K for Ni3Si and 600 K for Ni3Al. The apparent decrease in magnitude of the positive temperature dependence of strength in these alloys is then interpreted as stress relaxation which is found to become pronounced at higher test temperatures for finer grain sizes and for lower strain rates. It is concluded that grain boundary sliding is responsible for the stress relaxation and the activation energy for this thermally activated process is deduced to be 23 kJ/mol.
  • Recrystallization Texture

    pp. 1878-1887

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  • Influence of Solute Atoms in Solution and Precipitates on the Recrystallization in Iron and Low-carbon Steels

    pp. 1888-1897

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    Readers Who Read This Article Also Read

    1. Effect of Precipitation Behavior of AlN on Abnormal Growth of Ferrite Grains in Low-carbon Steel Wires Tetsu-to-Hagané Vol.70(1984), No.15
    2. Recent Development in the Research Technique on Recrystallization Tetsu-to-Hagané Vol.70(1984), No.15
    3. Deformation Structures as Nucleation Sites for Recrystallization Tetsu-to-Hagané Vol.70(1984), No.15
  • Recrystallization Behavior of Titanium and Its Alloys

    pp. 1898-1905

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  • Effects of Carbon on the Recrystallization Texture of Cold Rolled Sheet Steel

    pp. 1906-1913

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    The effects of carbon content below 46 ppm on the recrystallization texture were examined with a decarburized Al-killed steel of commercial purity. The carbon contents in the steel were varied by carburizing at 700°C before cold rolling or at 420°C after cold rolling, and then their recrystallization textures resulting from both cases were compared.
    The carbon content during annealing influenced the recrystallization textures when it ranged between zero and 20 ppm. The increase in the carbon content increased the amount of {110} components and decreased that of {100} components. This effect was believed to be caused by the carbon in solution. The carbon content during cold rolling was also found to have an influence on the recrystallization texture, when it exceeded 20 ppm. The increase in the carbon decreased the amount of {111} components and increased that of {110} components. This effect was thought to be due to the presence of iron carbide particles during cold rolling.
  • Recrystallization Behaviour and Textures in Extra-low Carbon Steel Sheets with Ununiform Distribution of Nitrogen Levels to the Plane Normal Direction

    pp. 1914-1921

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    Effects of nitrogen content and their diffusion on the recrystallization were investigated for extra-low carbon steel sheets (0.13% Mn). Decarburized sheets with three kinds of nitrogen level distribution to the plane normal direction(PN) were adjusted by atmosphere reaction ; (i) higher nitrogen level in surface layer than neutral layer (series A), (ii) uniform distribution (Series B) and (iii) inverse distribution to Series A (Series C). Each Series was classified into several average nitrogen contents(2-94 ppm). These were heavily cold-rolled and then annealed up to 750°C. Nucleation temperature was increased with average nitrogen content for each Series, while the 50%-recrystallization temperature was decreased with average nitrogen content for Series A and C. In the case of higher nitrogen content in average, the augmentation of (111) component by annealing process was large on both the neutral layer of Series A and the surface layer of Series C, where the grain growth to PN was frequently observed. It was inferred that the enhancement of (111) recrystallization textures was affected by the diffusion of nitrogen atoms dissolved from nitride on annealing stage.
  • The Effect of Silicon on Recrystallization Texture in Low Carbon Steel Sheets Containing Titanium

    pp. 1922-1929

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    The effect of silicon addition on the recrystallization texture of titanium-bearing sheet steel containing different amount of carbon in solution was investigated. The addition of silicon effectively developed {554}<225>recrystallization texture. This occurred when the specimen was annealed not only at a slow heating rate but also at a rapid heating rate. The changes in the annealing texture were regarded to have arisen as results of the effects of the decrease in solute carbon content and the stronger component of {111}<112> in the cold-rolled states.
  • Effect of Mn-S-O Balance on the Deep Drawability of Cold Rolled Steel Sheet

    pp. 1930-1937

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    The effects of Mn-S-O contents balance, carbide morphology, and size of MnS precipitate on the deep drawability of cold rolled steel sheet was studied.
    The obtained results are as follows.
    (1) In the case where the K-value [=Mn (%)-55/32 S (%)-55/16 O (%)] is about -0.1, the deep drawability of box annealed sheet is improved by low temperature coiling, because S remains in solution in hot bands. The deep drawability of the continuously annealed sheet is improved by high temperature coiling because S precipitates as sulfide. When the K-value lie between 0 and 0.1, these phenomena do not occur in low C rimmed steel sheet.
    (2) The improvement of the deep drawability of low C rimmed steel sheet by high temperature coiling in hot bands is not attributed to the growth of MnS precipitate but to the coarsening of carbide.
  • Effects of P and C Contents on the Recrystallization Texture and Drawability of Fe-P-C Alloys

    pp. 1938-1945

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    Using the method of crystal orientation distribution function analysis, recrystallization textures of high purity Fe-P-C alloys having widely different P and C contents were studied quantitatively.
    It was found that {554}<225> and {100}<011> components of the recrystallization texture exhibited similar dependence on P and C contents. At constant C content, both components increased with increasing P content. This increase occurred most markedly at 0.02%C. On the other hand, {110}<001> components of the recrystallization texture decreased with increasing P content.
    These changes in the recrystallization texture were found to depend strongly on the heating rate during annealing, this suggesting that some precipitation process was playing an important role in the texture formation. As a result of the formation of these recrystallization textures, the average Lankford's r value became maximum when P and C contents satisfied following conditions ; 0.1≥P≥0.01% and 0.03≥C≥0.01%.
  • On the Development of {111} Grains Through the Annealing in Cold Rolled Cu-bearing Low Carbon Steel Sheet

    pp. 1946-1953

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    A study has been made of the development of {111} grains through the annealing at slow heating in 1% Cu-bearing steels with two carbon levels, 0.04% and 0.002%. At the early stage of recrystallization, Cu precipitates of the 0.002%C steel disperse very finely compared with that of 0.04%C steel. These very fine precipitates of 0.002%C steel strongly inhibit the recrystallization of both {111} and {001} grains, resulting in the development of weak textures in sheet. Comparatively coarse precipitates of 0.04%C steel will allow the {111} grains to recrystallize easily, and recrystallized {111} grains grow into unrecrystallized {001} grains at the later stage of recrystallization, finally the strong {111} texture is developed in sheet. Such a difference in recrystallization behavior in Cu-bearing steel should be attributed to the dispersion size of Cu precipitates due to carbon content.
  • Mechanism of {111}-Texture Development by Controlled Cooling on Continuous Annealing

    pp. 1954-1961

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    The effect of the cooling rate during γ→α transformation on Lankford(r) values and textures has been investigated in low and extra-low carbon cold rolled steel sheets. (1) r-values increase, {111} textures develop and grain-sizes enlarge with decrease in the cooling rate during γ→α transformation in both steels. (2) These phenomena appear more distinctly in the extra-low carbon steel than in the low carbon steel. (3) Among the following steps(A) to (D), {111} texture develops most intensively during slow cooling step (D), (A) : during heating before γ-transformation, (B) : during heating after progress of γ-transformation, (C) : during holding and (D) : during slow cooling. (4) The development of {111} texture is suppressed by intermediate holding after rapid cooling at a low temperature in dual phase or at a high temperature in a single α-phase region. (5) These results can be reasonably explained by the application of the previous theory proposed by the author on the formation mechanism of α→γ→α transformation texture. That is, {111} texture develops as the results of the fact that the growth of residual α-grains is preferred to the nucleation of new α-grains during slow progress of γ→α transformation.
  • The Effect of Production Conditions on Grain Refinement for Stabilized Type Stainless Steel for Elevated Temperature Application

    pp. 1962-1969

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    Stabilized type stainless steel is processed to get finer grain size even at higher solutioning temperature. The detailed process is as follows. Carbides are fully dissolved at high softening temperature, and then, after cold work recrystalization is performed at lower solutioning temperature. Precipitation of fine carbides during the solution is proved to be responsible for the fine grain by preventing grain growth.
    SUS 347 HTB tubes (JIS) were made by the above process and examined for creep rupture. They showed higher creep rupture strength compared to the tubes with the lower softening temperature process. Advantage of this new process is to allow higher solutioning temperature which provides higher creep rupture strength.
  • Recrystallization Texture Formation of a Heavily Cold Rolled Cu-15at%Al Alloy

    pp. 1970-1976

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    On the basis of "TTT diagram for the recovery and recrystallization", the recrystallization process in a heavily cold rolled Cu-15at%Al alloy was studied by measuring X-ray diffraction intensities of the major components in the rolling and recrystallization textures. In order to investigate the effect of recovery, nucleation and short range ordering on the formation of the recrystallization texture, the alloy sheets were annealed with two-step process composed of primary annealing and secondary one at a temperature higher than the primary.
    The recrystallization process was retarded at temperatures below 540K. Two different values of the activation energy of the process were obtained in the temperature ranges below and above 540K, presumably due to the order-disorder transition. The two-step process enhanced the development of the major component of recrystallization texture when the primary annealing temperatures were below 600K, and the enhancement became stronger with decreasing the primary annealing temperatures.
    These results are discussed from the viewpoint of the competition between recovery, nucleation-growth and short range ordering in recrystallization.
  • Increase of Recrystallization Rate of Pure Copper by the Trace Addition of Ti, Zr or V

    pp. 1977-1983

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    The present authors previously reported that recrystallization of commercially available pure copper (oxygen free copper) was accelerated by the trace addition of Ti, Zr, Hf, V, Cr, Mn, or Fe. This study was undertaken to elucidate this phenomenon more clearly. Three sorts of pure coppers including the above and coppers with the trace addition of Ti, Zr or V up to about 50 mol ppm, etc. were used as specimens. Hardness and electrical resistivity measurements, structural observations, etc. were made mainly for coldworked or finally annealed specimens.
    The results of electrical resistivity measurements suggested that the additives should interact with a certain impurity in commercial pure copper. The recrystallization temperature of specially prepared pure copper with a sulfur impurity below 1 mol ppm extremely decreased, i. e. to a value of about 370K. A small number of dispersed fine particles were observed in the specimens containing the additives and a certain amount of sulfur. Based on the result of EDS analysis, they were a sulfide of additives. Therefore, the phenomenon was attributed to the fact that the amount of sulfur impurity dissolved in commercial pure copper was reduced by the trace addition of Ti, Zr or V.
  • Grain Growth in Single- and Dual-Phase Steels

    pp. 1984-1992

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  • Austenite Grain Refinement and Coarsening of Low Alloy Steel

    pp. 1993-2000

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  • Effect of Precipitation Behavior of AlN on Abnormal Growth of Ferrite Grains in Low-carbon Steel Wires

    pp. 2001-2008

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    Abnormal growth of ferrite grains in low-carbon steel wires (C<0.04%) was studied from the viewpoint of AlN precipitation during annealing after cold drawing of 70.2% in reduction.
    (1) Abnormal grain growth occurred when Al/N ratio of steel wires decreased to the range from 1 to 6.
    (2) AlN precipitation in wire rod within above range of Al/N ratio was delayed in the course of cooling after the hot rolling, followed with fine AlN precipitations during recrystallization and grain growth at annealing stage after drawing. Such precipitates generated a large restraining force on the grain boundary movement and grain growth was completely depressed. In the case of the isothermal annealing at 800°C, however, abnormal grain growth occurred in accordance with decrease in the restraining force as a result of the coalescence of AlN precipitates immediately after the precipitation had been completed.
    (3) The critical conditions investigated for the abnormal grain growth initiating in the restrained grains were in good agreement with HILLERT'S theoretical expectations.
    (4) The restraining force of the fine precipitates on the grain boundary movement can be evaluated as follows :
    s=f;(1-log f;2)σ/3r
    where s is the restraining force ; r and ƒ are radius and volume fraction of the second phase particles, respectively ; σ is the grain boundary energy.
  • Mechanism of the Formation of Columnar Structure in Low-carbon Steel Wires during Annealing

    pp. 2009-2016

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    Mechanism of the formation of columnar structure in low-carbon steel wires annealed at temperatures below A3-point was studied.
    (1) Columnar structure was developed in wires with medium reduction in area by cold drawing and annealed under a decarburizing atmosphere in the temperature range of α-γ two phase region.
    (2) Columnar grains were nucleated in the recrystallizaed grains a little below the surface layer of wires, and were characterized by their distinct preferred orientations and directional growth from the beginning of the grain growth.
    (3) Columnar structure exhibited nearly the same cylindrical texture as the recrystallized structure.
    (4) A mechanism was proposed for the directional growth of the columnar grains during annealing in the α-γ region : Small recrystallized grains with a cylindrical texture are rearranged into small blocks of grains with a same orientation in the course of γ/α transformation which takes place by decarburization. A large growing grain neighboring these blocks continues its growth by coalescence with the blocks. The activation energy for this process is considered to be less than a process in which each small grain coalesces individually into a large grain.
  • Recrystallization and Grain Growth in Formation of Dual-phase Structure in Cu-4% Ti Alloy

    pp. 2017-2024

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    Fine dual-phase structure consisting of recrystallized α-Cu grains and Cu3Ti precipitates at grain boundary corners is obtained in a Cu-4% Ti alloy by the following processing : solution treatment, heavy cold work and annealing. Details of deformation structure, interaction between recrystallization and precipitation and kinetics of grain growth in the dual-phase structure, have been investigated by means of transmission electron and optical microscopy. The results are as follows. (1) The formation of the dual-phase structure occurs at cell structure in cold-rolled specimems. (2) Recrystallization of α-Cu phase and precipitation of Cu3Ti particles proceed simultaniously in the early stage of annealing at 750°C, and Cu3Ti particles located at the grain boundary corners grow preferentially during further annealing. On the other hand, high density of titanium rich zones first precipitate during annealing below 650°C. and recrystallization process is retarded by the zones. Heterogenious precipitation of Cu3Ti particles at the cell walls causes dissolution of the zones and accerelates recrystallization. The lower the annealing temperature, the finer dual-phase structure is formed. (3) Relations between mean radius, R and annealing time, t in grain growth of α-Cu and Cu3Ti phases, are both described by the following equation, R4-R40=kt.
  • Grain Growth in Duplex Stainless Steels

    pp. 2025-2032

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    Grain radii of α and γ phases in duplex stainless steels annealed at 1 000 -1 200°C have been measured, and the growth mode of α and γ grains has been investigated. The results obtained are as follows :
    (1) The grain size of duplex stainless steels is much finer than those of α and γ single phase stainless steels. This is caused by the facts that α and γ grains restrict the growth of partner's grains by the pinning effect, and the growth mode of both grains becomes similar to the Ostwald ripening.
    (2) In α-rich duplex stainless steels, the grain growth of both α and γ phases is controlled by volume diffusion in the α phase, and is described by the third power law (R3-R30=k3t).
    (3) In γ-rich duplex stainless steels, the grain growth is controlled by the diffusion along grain boundary of γ phase, and is expressed by the fourth power law (R4-R40=k4t). If the volume fraction of α phase is smaller than 0.1, however, α grains are mostly located within γ grains, and the grain growth is controlled by volume diffusion, obeying the third power law.
    (4) The grain radius of major phase, R is related to the grain raius, r and the volume fraction of minor phase, ƒ through the Zener's relation (Rr/f;). The coefficient β is nearly 4/9, which has been proposed by HELLMAN and HILLERT.
  • Mechanism of Secondary Recrystallization in Grain Oriented Silicon Steel

    pp. 2033-2040

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  • The Influence of Very Finely Dispersed Carbides on Primary Recrystallization Texture in 3.3% Si Steel

    pp. 2041-2048

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    The primary recrystallization texture of 3.3% Si steel containing 0.040% carbon was studied with interest in the effect of the states of carbon prior to cold rolling. The following four states of carbon were obtained by changing cooling way after annealing, that is, carbon in solution, very finely dispersed carbides (10-50 nm), finely dispersed carbides (100-300 nm) and coarse carbides on grain boundaries. The specimens treated in the above conditions were cold rolled 60% and then annealed at 800°C.
    The very finely dispersed carbides had the strongest effect on promoting dislocation tangling at cold rolling stage, recrystallization at heating stage, and thereby formation of (110) [001] recrystallization texture. The possible mechanisms for this result are as follows. (1) The very finely dispersed carbides are optimum with respect to size and distribution to yield dislocation pile-up, resulting in formation of deformation bands. (2) They are dissolved and disappear at later stage of cold rolling or heating stage of subsequent annealing. (3) They contribute to preferred nucleation by (1) and to growth of (110) [001] grains by (2).
  • Improvement of Magnetic Properties by Cu Addition in Grain-oriented Silicon Steel

    pp. 2049-2056

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    There are a few reports that Cu sulfides precipitate with the addition of Cu in the grain-oriented silicon steel, but the precipitates of Cu sulfides have not yet been well observed Thus, the observation of the precipitation of Cu sulfides is performed and the metallurgical effects of Cu addition on the grain-oriented silicon steel are studied.
    (1) With the addition of small amount of Cu, fine particles of (Cu, Mn) 1.8S (size 200500Å) precipitate and inhibition effects of normal grain-growth are enhanced. The distribution of Cu sulfides in hot rolled sheets provides beneficial geometrical situation to grow sharp Goss grains selectively during the secondary recrystallization.
    (2) In the texture at the subsurface of hot rolled sheets, {110} (001) grains are increased, and after decarburization, {554} <225> and {110} <001> grainsare increased, on the other hand {100} <001> grains are decreased. These make secondary recrystallization easy.
    (3) When small amount of Cu is added and cold rolling reduction is increased from 55% to 65%, there are improvements of magnetic properties of grain-oriented silicon steel.
  • Formation of the Goss Texture in Grain Oriented Silicon Steel Containing a Small Amount of Molybdenum

    pp. 2057-2064

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    Transmission KOSSEL(TK) technique has been applied in an attempt to elucidate the origin of the potential nuclei of the celebrated (110) [001] secondary grains in hot-rolled sheets of high induction grain oriented silicon steel with or without a small amount of Mo. In the microstructure in the vicinity of the surface of the hot-rolled sheets, the development of the recrystallized grains is much more noticeably retarded and the polygonized {110} <001> grains elongated to the rolling direction are more preferentially formed in Mo added steel than in that of free from Mo. By TK measurement, two kinds of polygonized {110} <001> grains are found at the 1/10 depth ; large polygonized (110) [001] grains containing the highly oriented (110) [001] areas with sharpened TK patterns and small polygonized {110} <001> grains with all the diffused TK patterns. The potential nuclei of (110) [001] secondary grains can be inherited by the structure memory from the highly oriented (110) [001] areas within the former large polygonized (110) [001] grain. The frequency of generation and the rate of occupation of (110) [001] secondary nuclei of the hot-rolled sheet containing a small amount of Mo are approximately three times larger than those of free from Mo. It is considered that grain oriented silicon steel containing a small amount of Mo is more effective in the development of (110) [001] secondary grains having small grain sizes.
  • Effect of Cold Rolling on the {110} <001> Secondary Recrystallization in 3% Silicon Steel

    pp. 2065-2072

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    Cold rolling is a primary process for producing the texture of {110} <001>in 3% silicon steel. Two types of experiments are made to evaluate the role of cold reduction. One is the change of rolling direction between cold rolling and hot rolling. Heavy cold reduction of 87% resulted in highly prefered orientation of the {110} <001> secondary recrystallized texture regardless of the cold rolling direction, whereas lower cold reduction of 70% led to deviation of <001> axis to the hot rolling direction.
    The second experiment is cold rolling with grooved roll during the early stage of cold rolling. Cold reduction with grooved roll led to the occurrence of smaller secondary grains with {210} <001> and {310} <001> orientations among the large {110} (001) grains resulting in smaller average grain size as compared to the ordinary case.
  • Microstructural Characteristics of Dynamic Recrystallization and Its Comparison with Static Recrystallization

    pp. 2073-2080

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    Readers Who Read This Article Also Read

    1. Effect of Precipitation Behavior of AlN on Abnormal Growth of Ferrite Grains in Low-carbon Steel Wires Tetsu-to-Hagané Vol.70(1984), No.15
    2. Recent Development in the Research Technique on Recrystallization Tetsu-to-Hagané Vol.70(1984), No.15
    3. Deformation Structures as Nucleation Sites for Recrystallization Tetsu-to-Hagané Vol.70(1984), No.15
  • Recrystallization in Hot Working

    pp. 2081-2089

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  • Origin and Development of Inhomogeneous Structure in Rolled Steel Sheets

    pp. 2090-2096

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  • Orientation Relationships between Grains during Dynamic Recrystallization of Polycrystalline Nickel

    pp. 2097-2103

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    Microscopic observation on dynamic recrystallization in polycrystalline nickel and the orientation analysis of individual grains have been conducted by using electron channeling patterns.
    Originally existing grain boundaries began to bulge out at a strain of 0.5εp and new grains began to come out along grain boundaries at a strain of 0.75 εp, where εp is the peak strain corresponding to a maximum flow stress. It was found that only a few grains were produced by a bulging or a multiple twinning process. This is at variance with the observations on single crystals or a coarse-grained austenitic steel.
    The growth rate of new grains was seemingly independent of the orientation relationships in their growth fronts. This trend is in contrast to the static recrystallization. The reason for this difference is discussed in special reference to the concurrent straining during the recrystallization.
  • Effect of Rolling Strain Rate on the Grain Size of Austenite Recrystallized Immediately after Hot Rolling

    pp. 2104-2111

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    The effect of rolling strain rate on the grain size of austenite recrystallized immediatelly after hot rolling was investigated in the temperature range of 1 000 to 1 200°C. An increase in roll speed and/or a decrease in the specimen thickness before reduction was found to contribute to the refinement of recrystallized austenite grains. It suggested that austenite grain size also changed with roll radius. These results indicate that austenite grain size depends on roll radius, roll speed, and the slab thickness, in addition to generally known factors such as rolling temperature, rolling reduction, and initial grain size. It is known that recrystallized austenite grain size after hot rolling is well related with rolling reduction when rolling temperature and initial grain size are held constant. In this experiment where the specimen thickness before reduction, roll speed, and roll radius were variable factors, a good correlation was obtained between austenite grain size and rolling strain rate. We found that austenite grain size number (N) was hardly affected by the alloying elements such as C, Mn, Nb, V, Mo, and Ti, but was approximately related to rolling strain rate (ε) by :
    N=-8.3ε-1/2+0.33N0+0.010(1 200-T)+8.8
    where N0 is initial grain size number and T is rolling temperature.
    ε=2πn/60√r·√R/H0·ln(1/1-r)
    where n is roll speed (rpm), r is rolling reduction, R is roll radius (mm), and H0 is thickness before reduction (mm).
  • Structure of Austenite of Carbon Steels in High Speed Hot Working Processes

    pp. 2112-2119

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    In this investigation, the recrystallization behaviour of austenite of carbon steels due to hot working has been studied. To investigate the change of structure of austenite during hot rolling of strip, a newly developed testing machine which enables simulations of hot rolling of plate, strip and wire rod has been used. The results of the experiments have been evaluated to make a calculation model of grain size and fraction recrystalized. The feature of this calculation model is that the effect of prior working on the recrystallization behaviour at next deformation can be quantitatively taken into consideration by means of dislocation density of material.
    The accuracy of the model has been examined by experiments of single pass rolling in laboratory and by wire rod rolling in practice. A reasonable agreement is obtained in most cases. The model is used to estimate the influence of rolling temperature, speed of strip, initial grain size, and schedule of reduction on the grain size after final rolling of hot strip.
  • Metallurgical Factors Influencing Microstructure of Hot Rolled Ultra Low C Steel

    pp. 2120-2127

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    Influence of processing variables on microstructure of hot-rolled ultra low C Al-killed steel containing 30 ppm C was investigated by comparing with the results for 0.006%C and 0.02%C steels. In this study, a 150 t TMT (Thermomechanical treatment) simulator capable of multi step working at high strain rate was used.
    Ferrite grain diameter increased remarkably as the amount of C decreased from 0.006% to 0.003%, while dependence of α grain size on the final working temperature changed little with C content. Cooling rate after the hot working had great effect on the grain size, especially in the range from 10 to 30°C/s in 0.003%C steel. The effect of reduction percent in final hot working on the grain size was small. Grain growth of ferrite hardly occurred even under the isothermal holding condition of 800°C×1h. It was observed in 0.003%C steel that large columnar grains elongated in the direction of thickness were formed near under the surface, it depending on the cooling rate.
    Metallurgical factors controlling these characteristic microstructures in ultra low C steel were discussed in terms of as heated γ grain size, γ grain growth, γ grain refinement through recrystallization, γ/α grain size change in transformation and α grain growth at higher temperature.
  • Recrystallization of Austenite of Carbon Steel in Sequential Hot-rolling

    pp. 2128-2135

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    In order to clarify the structural change during high-speed sequential hot rolling, the prior-austenitic microstructures of quenched carbon steel with 0.44 to 0.83%C content were studied by (a) mill-motor-stop experiment in a wire-rod mill, (b) experimental one-pass high-speed rolling and (c) hot deformation simulator experiment. From the results it was concluded as follows :
    1) After passing through a train of wire-rod rolling, austenite is fully recrystallized and the grain diameter, d, is approximately predicted from ZENER-HOLLOMON parameter Z, d reducing with higher Z.
    2) Especially in higher Z, the grain diameter is larger than that of dynamically recrystallized austenite, possibly showing the contribution of static growth of grain after partial dynamic recrystallization.
    3) Even in lower Z, the distribution of the grain diameter is positioned to the larger side of the dynamically recrystallized grain. This phenomenon is possibly due to the grain growth after dynamic recrystallization.
    4) The fraction of recrystallization is higher in the wire-rod rolling than in the simulator experiment. This possibly shows the effect of additional strain in the caliber rolling.
  • Occurrence of Coarse Grains in Hot-rolled Low Carbon Aluminium Killed Steel Sheets Coiled at High Temperature

    pp. 2136-2143

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    The occurrence of coarse grains in hot-rolled low carbon aluminium-killed steel sheets coiled at high temperature was studied.
    The relation between microstructures and hot rolling conditions was investigated on the basis of hot rolling experiments in the laboratory.
    Fine grain bands form by finish-rolling below the Ar3 temperature, and they change to coarse grain bands by abnormal grain growth. They form at the surface of sheet when the finishing temperature is close to Ar3, and extend to its center in thickness with lowering the finishing temperature.
    Aluminum nitride begins percipitating rapidly at grain boundaries after finish-rolling. This compound is the main precipitate pinning grain boundary. But the abnormal grain growth proceeds mostly before the grain boundaries are pinned firmly by the precipitation of AIN.
    These results were confirmed in the hot rolling experiments in the shop.
    x

    Readers Who Read This Article Also Read

    1. Effect of Precipitation Behavior of AlN on Abnormal Growth of Ferrite Grains in Low-carbon Steel Wires Tetsu-to-Hagané Vol.70(1984), No.15
    2. Recent Development in the Research Technique on Recrystallization Tetsu-to-Hagané Vol.70(1984), No.15
    3. Deformation Structures as Nucleation Sites for Recrystallization Tetsu-to-Hagané Vol.70(1984), No.15
  • Influence of Hot Rolled Microstructure on the Recrystallization at Surface Layer of Cold Rolled Low Carbon Steel Sheets

    pp. 2144-2151

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    Influence of hot rolled microstructure on the recrystallization behavior at surface layer of cold rolled low carbon steel sheets was studied by optical microscopic and X-ray reflection techniques. The main results obtained are as follows. 1) Recrystallization at surface layer delays in comparison with interior region, and it depends mainly on {001} <110> developed at the surface layer by cold rolling. 2) Delay of recrystallization is more remarkable at coarser grains in hot rolled steel sheets. It is considered that the delay is attributed to the effect grain size on the recrystallization and the promotion of formation of {100} in coarse grains. 3) The surface texture of cold rolled sheet forms in very thin layer, about 2.5% from surface in thickness, and the formation of {100} is faster than that of {111}.
  • Formation of Deformation Band and Static Recrystallization Behavior of Hot Rolled Fe-19%Cr Ferritic Alloy

    pp. 2152-2159

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    The effects of initial grain size (1 000μm and 430μm), rolling temperature and reduction on the deformation structure and recrystallization behavior of a hot rolled Fe-19%Cr ferritic alloy were investigated. The characteristics of the deformation band formed by hot rolling and its effect on recrystallization were crystallographically studied. The main results are as follows.
    (1) Above 1 000°C well defined subgrain substructures are observed. With increasing temperature, the subgrain size increases. In specimens hot rolled below 1 100°C, deformation bands are observed preferentially near grain boundary.
    (2) The number of deformation bands increases with increasing rolling reduction or decreasing grain size. The deformation band and the matrix are correlated with a rotation in the range of 35°-55° around a <110> common axis. The orientations of deformation band and matrix are nearly <100>//N.D and <211>//N.D, or <211>//N.D and <100>//N.D The subgrain size of <100>//N.D orientation is coarse, compared with those of other orientations.
    (3) The recrystallization occurs preferentially in the boundary area containing deformation bands. Recrystallized grains have almost the same orientation as the matrix or the deformation band. Decreasing the rolling reduction retards recrystallization, especially in coarse grained specimens. The retardation is attributed to the decrease of deformation bands.
  • Static Restoration after Hot Deformation of a 2.9% Si Steel

    pp. 2160-2167

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    Static restoration process was investigated quantitatively for the 2.9% Si steel deformed in tension for the temperature range from 1 003 K to 1 173 K and for the strain rate range from 0.02 s-1 to 18 s-1. Recrystallization is strongly accelerated by increasing strain in the low strain region. The acceleration results not only from the increase of dislocation density with increasing strain but also from the progressive formation of uniform subgrain structures by dynamic recovery. These results suggest that recrystallization in dynamically recovered structure is faster than that in the strain hardened structure at low strains or the structure deformed at low temperatures, if dislocation densities in the both are about the same.
    Most of recrystallized grains occured "in colonies" along the original grain boundaries when the fraction of recrystallization, X, is 0.03. With an increase in X the number of nuclei increased when X≅0.1 and then decreased to about half of the maximum value (at X≅0.1), which was almost constant in the range of X from 0.2 to 0.6. When X≤0.6 the retarding effect of recrystallization by static recovery was almost negligible, but when X≥0.6 it appeared clearly. This effect is caused by the decrease of dislocation density in subgrains and the growth of subgrains in the latter stage of recrystallization.
    Temperature dependence of the rate of recrystallization was measured under the same flow stress in high strains. The activation energy for recrystallization is 215 kJ/mol and that for grain growth is 230 kJ/mol. Both the values are almost the same with that for self-diffusion of iron atom in a 2.9% Si steel. The rate of recrystallization is concluded, therefore, to be controlled mainly by the growing velocity of new grains.
  • Superplasticity of δ-ferrite/austenite Duplex Stainless Steels

    pp. 2168-2175

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    Superplastic behavior of δ-ferrite/austenite duplex stainless steels has been studied by means of isothermal hot tensile test at temperatures (T) from 700 to 1 100°C at initial strain rates (ε) from 10-4 to 10-1s-1 with particular emphasis on microstructural aspect prior to and during deformation. Large elongations are observed in the wide renges of T and ε. The maximum value, above 2 500%, is obtained under the condition that σ phase precipitation occurs. The elongation depends on the precipitation rate of σ phase especially in the lower temperature deformation as well as on the prior microstructure. The most suitable prior microstructure can be obtained by refining δ-ferrite matrix as well as fine dispersion of γ particles. In the deformation of the specimens with such optimum conditions, even if ε_??_10-1s-1, large elongations above 200 % can be observed at T≅1 000°C. During superplastic flow, the microstructure largely changes, i.e, at above 1 000°C γ phase is separated and refined into spheroidized particles within the δ-ferrite matrix and at below 1 000°C γ/σ mixed structure is formed by the eutectoid decomposition from δ-ferrite, resulting finally in the stable equiaxied micro-duplex structures with δ/γ and γ/σ, respectively. Such microstructural changes can play an important role for the superplastic behavior in addition to the effect of m-value.

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