Tetsu-to-Hagané
New Arrival Alert : OFF

You can use this feature after you logged into the site.
Please click the button below.

Log in / Sign up
ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Advance Publication

  • Thermal Stability of Resistance to Propagation of Mechanically Small Fatigue-cracks in a Fe-N Binary Ferritic Steel

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2355/tetsutohagane.TETSU-2019-091

    We investigated the effect of solute nitrogen on threshold stress intensity factor range, ΔKth, of the growth of small cracks using a water-quenched Fe-0.011N (wt.%) binary alloy, in terms of strain-age hardening. Fatigue tests were carried out for micro-notched specimens at 20°C and 160°C at a frequency of 30 Hz with a stress ratio of –1. The nitrogen effect on ΔKth at room temperature was significant, but smaller than the carbon effect. On the other hand, the thermal stability of the strain aging effect on ΔKth was higher in the Fe-0.011N steel than in Fe-C steels containing supersaturated carbon, because the nitrogen solubility above room temperature is higher than the carbon solubility in ferritic steels.
  • Behavior of Crack Generation of Slag in Continuous Solidification Process of Blast Furnace Slag

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2355/tetsutohagane.TETSU-2019-084

    A continuous solidification process of blast furnace slag was developed to promote the use of air-cooled slag coarse aggregate for concrete. In this process, the molten slag can solidify in only 120 s and the slag thickness is about 25 mm. This process suppresses gas generation and greatly reduces water absorption. Most of the slag is crystalline, and part of the slag has a glass layer on its surface. Slag with a glass layer is brittle because it contains several cracks. Therefore, microscopic observation and thermal stress analysis of the solidified slag were carried out to clarify the mechanism of crack generation in the plate-like slag. In the microscopic observation, several cracks with a length of about 8 mm were found in the slag with the glass layer. From the analysis, in the cooling pattern of the slag on the piled slag a temperature difference of about 200 K exists between the center and the mold side in the slag pit, and keeping this difference results in tensile stress of more than 50 MPa. However, in the cooling pattern of the crystalline slag in the piled slag, the temperature gradient in the slag in the slag pit was very small because the slag was retained in the piled slag, and as a result, the thermal stress was almost 0 MPa.
    x

    Readers Who Read This Article Also Read

    1. Segregation Mechanism of Al-based Oxides on Surface of Zn-0.2mass%Al Hot-dip Galvanized Steel Sheets ISIJ International Advance Publication
  • Peritectic Structure Evolution in Hot-dip Zn-Al alloy coatings

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2355/tetsutohagane.TETSU-2019-107

    The present study investigated the microstructure in hot-dip Zn-(11, 22, 30)%Al coating steel sheets in order to clarify their solidification microstructure evolution process. There are two kinds of Zn-Al binary phase diagrams. One includes peritectic reaction but another doesn’t. In the Zn-Al binary phase diagram including peritectic reaction, the peritectic reaction occurs when the Al content is higher than 13%. In fact, the peritectic structure was formed in dendrites of the hot-dip Zn-(22, 30)%Al coating steel sheets, but not in the hot-dip Zn-11%Al coating steel sheets. This indicates that the Zn-Al binary phase diagram including peritectic reaction is suitable for understanding the solidification microstructure evolution of hot-dip Zn-Al alloy coating steel sheets.
  • Evaluation of Hydrogen-induced Cracking Behavior in Duplex Stainless Steel by Numerical Simulationof Stress and Diffusible Hydrogen Distribution at the Microstructural Scale

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2355/tetsutohagane.TETSU-2019-101

    Duplex stainless steels have ferrite and austenite microstructures, which have material properties that are different. The strength level and hydrogen diffusion constant of the phases are different; therefore, it is expected that the microscopic stress and hydrogen concentration distribution are inhomogeneous. Assuming that hydrogen-induced cracking occurs at locally stress-concentrated and hydrogen accumulated locations, it is important to take into consideration the influence of the microstructure in the evaluation of hydrogen-induced cracking. In order to observe crack locations at the microstructural scale, a slow strain rate test of hydrogen-charged specimen was performed and the cross section of the specimen was observed after the test. Hydrogen-induced cracks were mainly found in the ferrite phase. In order to clarify the contribution of the stress and hydrogen concentration distribution to the initiation of hydrogen-induced cracks, a numerical simulation was performed. A microstructural-based finite element model consisting of ferrite and austenite phases was designed based on the micrograph of the duplex stainless steel used. Stress–strain curves of the ferrite and austenite phase were set and macroscopic tension was applied to calculate the microscopic stress distribution. Incorporating the stress distribution into hydrogen diffusion simulation as one of driving forces, the microscopic distribution of hydrogen concentration was calculated. From the simulation results, stress concentration and hydrogen accumulation occurred at ferrite phase or ferrite/austenite boundary. This tendency corresponds closely to the experimentally observed results; therefore, the above approach can be applied to the evaluation of hydrogen-induced cracking at the microstructural scale.
  • Numerical Simulation on Effect of Microstructure on Hydrogen-induced Cracking Behavior in Duplex Stainless Steel Weld Metal

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2355/tetsutohagane.TETSU-2019-102

    Duplex stainless steels and their deposited weld metal have ferrite and austenite microstructure, which have material properties that are different. In addition, the microstructure of the base metal and weld metal are clearly different; therefore, it affects the hydrogen diffusion and accumulation, and hydrogen-induced cracking behavior at the microstructural scale. In this study, the influence of the microstructure on hydrogen-induced cracking behavior of duplex stainless steel weld metal was investigated. Specimens of duplex stainless steel weld metal were prepared and slow strain rate tensile test was performed after hydrogen charging. Cracks were observed at boundaries of ferrite and austenite phases. In order to clarify the stress and hydrogen concentration distribution at the microstructural scale, a microstructure-based finite element simulation was performed. A finite element model based on a cross sectional observation of the microstructure was designed to calculate the stress and hydrogen concentration distribution. The simulation result showed that the hydrogen accumulation occurs at ferrite/austenite boundaries, which corresponded to the locations where cracks were observed in the experiment. On the other hand, the hydrogen concentration at the accumulation site in the weld metal was low compared to that in the base metal. Therefore, the influence of the phase fraction and the stress-strain curves of the ferrite and austenite phases on the hydrogen concentration was investigated by the proposed numerical simulation. It was demonstrated that both the phase fraction and stress-strain curves have significant influence on the microscopic distribution of hydrogen concentration.
  • Recrystallization Behavior and Formation of {411} <148> Grain from α-fiber Grains in Heavily Cold-rolled Fe-3%Si Alloy

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2355/tetsutohagane.TETSU-2019-086

    Recrystallization texture is essential to control the mechanical and magnetic properties of steels. Both γ-fiber (ND//<111>) and α-fiber (RD//<011>) textures are known to develop during the rolling process of bcc iron. Recrystallization behavior from γ-fiber has been extensively studied. On the other hand, recrystallization behavior from α-fiber, in particular after heavy cold rolling reduction, has not been sufficiently clarified. In this study, recrystallization behavior from α-fiber, focusing on the formation of {411}<148> recrystallized grain, was investigated by means of EBSD and TEM. {411}<148> region already existed in the vicinity of deformed grains having upper α-fiber orientation ({100}<011> ~ {211}<011>). TEM observation revealed the existence of the lamellar structure with {411}<148> relatively fine dislocation cells in the {211}<011> deformed grains. With the progress of the recovery, {411}<148> subgrains (dislocation cells) are postulated to easily form and are surrounded by the deformed matrix grains with high angle interface. Thus, it is easy to form the recrystallization nuclei having the potential to grow with the sake of both high driving force and high interface mobility. At the early stage of recrystallization, {411}<148> recrystallized grains developed in {211}<011> deformed grains. At the later stage, {411}<148> recrystallized grains from {211}<011> deformed grains encroach {100}<011> deformed grains and new {411}<148> recrystallized grains developed in {100}<011> deformed grains.
  • Friction Property under Lubrication for Case Hardening Steel Subjected to Combined Thermomechanical Treatment with Excess Vacuum Carburizing and Subsequent Severe Plastic Deformation and Induction Hardening

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2355/tetsutohagane.TETSU-2019-082

    Friction property of the case hardening steel subjected to excess vacuum carburizing and subsequent severe plastic deformation and induction hardening was evaluated by the traction test. The purpose of this study is to clarify the effect of fine microstructure on the friction property, focusing on the interaction between the fine microstructure and the lubricating oil additives. The vacuum carburizing treatment is performed at the hyper-eutectoid composition of 1.0 mass% C. Subsequently, the carburized surface was formed the white layer by the surface-nanostructured wearing (SNW) process, and the specimen having the initial microstructure was subjected to induction hardening. The microstructure of the condition with SNW was finer compared to that with SNW-less. According to the traction test, traction coefficient (μ) in the specimen having the fine microstructure on the rolling contact surface decreased. Therefore, it was found that the decrease of μ could be achieved by the application of high-density lattice defects (grain boundaries in this study). After the test, the rolling contact surface of the specimen with fine microstructure became smooth, and the surface showed high reactivity with the lubricating oil additives and formed the compound film of Fe-O-P system having a fine, spherical morphology. The surface roughness was improved by the presence of the wear particles on the surface. Therefore, it was thought that the μ was decreased because the transition to a mild friction condition was caused due to the dispersion of the contact pressure.
  • Crystal Structure Analysis of Top Dross in a Molten Zinc Bath by First Principle Calculation and Synchrotron X-ray Diffraction

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2355/tetsutohagane.TETSU-2019-088

    In a molten zinc bath in a continuous galvanizing line, top dross particles crystallize as Fe2Al5 intermetallic compound containing Zn, which causes the surface defect of the final products by easily adhering to steel sheets. The present study focused on the analysis of crystal structure of the top dross by simultaneously exploiting first principle calculation and synchrotron X-ray diffraction of top dross prepared in a laboratory. The following results were obtained: The first principle calculation on top dross suggested that two Al atoms in the partially occupied four Al sites of Fe2Al5 based on the crystal structure proposed by Mihalkovič et al. were replaced by two Zn atoms. In addition, Al atoms in the two kinds of partially occupied Al sites in Fe2Al5 proposed by Burkhardt et al. was equally replaced by Zn atoms. The propose crystal structure of top dross was verified by the X-ray diffraction profile analysis using RIETAN-FP simulation as well as the experimentally determined lattice constant of Zn containing top dross.
  • Mechanism of Improved Ductility of 1,500 MPa-class Ultra-high Strength Cold-rolled Steel Sheet Produced by Rolling and Partitioning Method

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2355/tetsutohagane.TETSU-2019-083

    By using a steel with standardized chemical composition and conventional manufacturing processes for flat-rolled steel strip, a 1,500 MPa class stainless steel sheet whose product of yield strength (YS) and total elongation (El) exceeds 30,000 MPa% was developed and its mass production has been established.Besides the excellent YS-El balance, the developed steel sheet has excellent performance for not only an anti-secondary work embrittlement but also high cycle fatigue endurance.Core technology of the developed method is composed of a combination of high precision cold-rolling and isothermal partitioning treatment in a batch furnace, the name of which was called Rolling and Partitioning (R&P) method. By the R&P method, the microstructure of steel is controlled to the mixture of a strain induced martensite as the matrix phase, and an optimum amount of retained austenite as the second phase which is dispersed in isolation and surrounded by the transformed martensite.In this paper, the microstructure formation during the R&P process and the deformation mechanism that would bring about the excellent strength-ductility balance are discussed based on the results obtained from the in-situ neutron diffraction measurement. The results have revealed that the typical Lüders-like stress-strain curve of R&P steel is caused by competitive plastic flow between austenite and martensite, and an effective transformation induced plasticity phenomenon.

Article Access Ranking

27 Feb. (Last 30 Days)

  1. Segregation Mechanism of Al-based Oxides on Surface of Zn-0.2mass%Al Hot-dip Galvanized Steel Sheets ISIJ International Advance Publication
  2. Perspective toward Long-term Global Goal for Carbon Dioxide Mitigation in Steel Industry Tetsu-to-Hagané Vol.105(2019), No.6
  3. Preface to the Special Issue “Intelligent Abnormality Diagnosis for Steel Works by Using Area Sensing” Tetsu-to-Hagané Vol.106(2020), No.2
  4. Effect of Silicon, Manganese and Heating Rate on the Ferrite Recrystallization Kinetics ISIJ International Advance Publication
  5. Multiscale Analysis of MnS Inclusion Distributions in High Strength Steel ISIJ International Advance Publication
  6. In-situ Phase Identification of Crystallized Compound from 2CaO·SiO2–3CaO·P2O5 Liquid ISIJ International Advance Publication
  7. A Data-Driven Multiobjective Dynamic Robust Modeling and Operation Optimization for Continuous Annealing Production Process ISIJ International Advance Publication
  8. Physico-chemical Properties of Mill Scale Iron Powders ISIJ International Advance Publication
  9. Numerical Simulation of Impinging Gas Jet on a Liquid Bath Using SPH Method ISIJ International Advance Publication
  10. A Review on Prevention of Sticking during Fluidized Bed Reduction of Fine Iron Ore ISIJ International Vol.60(2020), No.1

Search Phrase Ranking

27 Feb. (Last 30 Days)

  1. blast furnace
  2. blast furnace productivity
  3. blast furnace permeability
  4. corrosion resistant steel
  5. ferrite bainite steel
  6. low cycle fatigue
  7. stainless steel
  8. titanium
  9. damage
  10. damage model