Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 66 , Issue 6
Showing 1-20 articles out of 20 articles from the selected issue
  • Yuuzou Kawahara
    2002 Volume 66 Issue 6 Pages 543
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Download PDF (141K)
  • Takanori Matsui, Koumei Kato, Yasuo Dotani, Yuuzou Kawahara, Yoshiyasu ...
    2002 Volume 66 Issue 6 Pages 544-548
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    A Ni-Cr-Mo alloy, JHN-24 has been developed as a new superheater tube material for advanced waste incinerator. In order to evaluate its thermal stability, microstructure and mechanical properties were investigated before and after thermal exposure. In solid solution condition, the microstructure consisted of fcc γ single phase and this alloy was able to keep relatively high strength up to 550°C. The changes in microstructure and mechanical properties were observed after thermal exposure. In the temperature range 450-550°C, as exposure temperature and time increase, tensile strength, 0.2% yield strength increased and elongation, reduction of area decreased. However the alloy sustained higher than 40% in elongation and reduction of area under any exposure condition. Moreover it was confirmed that impact strength decreased as temperature and time increased in the temperature range 500-550°C but was higher than 160 J/cm2 under any conditions. Transmission electron microscopy observation revealed that Pt2Mo-type intermetallic compound precipitated in fine and uniform condition. It was suggested that Pt2Mo-type intermetallic compound phase which was coherent with γ matrix didn’t show harmful effect as μ and P phase.
    Download PDF (875K)
  • Yuji Fukuda, Yuuzou Kawahara, Masaki Nakamura, Tooru Shimada
    2002 Volume 66 Issue 6 Pages 549-553
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    A regression analysis was conducted on corrosion rate of alloys tested in three typical domestic waste-to-energy plants. In this analysis, corrosion rate was assumed to follow parabolic or linear law and the rate constants were determined as a function of five independent variables, i.e., gas temperature, metal temperature, HCl concentration in the flue gas, Cl concentration in the ash deposit and the summation of Cr, Ni and Mo content in the alloys. The regression analysis of the predicted and observed corrosion rate constants showed an approximate 1:1 relationship for both linear and parabolic rate law with a correlation coefficient of 0.8. However, on the basis of comparison between the calculated and observed values in the pilot plant, the regression equation was modified. As a result, simple mathematical equations were derived, which are capable of predicting the corrosion rate of superheater tubes used in waste-to-energy plants.
    Download PDF (394K)
  • Atsushi Sho, Tatsuro Isomoto, Kazuhiro Toyama, Takeo Urabe, Masayuki Y ...
    2002 Volume 66 Issue 6 Pages 554-562
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    In order to realize the high-efficiency municipal solid waste(MSW)-to-power generation, an actual plant test of newly developed 20Ni-25Cr stainless steels added 3%Si together with the other conventional superheater tube materials was conducted in an MSW incineration plant in Tokyo. To confirm the effect of Si on high-temperature corrosion, the corrosion performance of developed steels was evaluated at 450 to 500°C for metal surface temperatures with considering the effect of flue gas and steam temperatures, through the detail investigation of various characteristics such as chemistry of the flue gas and ash deposits. The localized corrosion behavior of developed steels was also evaluated. It was proved that adding Si to 20Ni-25Cr stainless steels was also effective in this actual test, and developed steels had a good corrosion resistance rather superior to the conventional 20Ni-25Cr steels, probably due to the combined Cr and Si oxide layer. Moreover, corrosion behavior of welds, which exhibited different modes of corrosion failure, was also evaluated in terms of flue gas and steam temperatures.
    Download PDF (1234K)
  • Yuji Fukuda, Yuuzou Kawahara
    2002 Volume 66 Issue 6 Pages 563-568
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Protective coatings produced by high velocity flame sprayings can be useful in resisting the hot corrosion experienced in waste incinerators. The D-Gun and HVOF coating processes produce poreless high quality coating layers with strong adherence to substrate materials. Laboratory tests were performed to examine corrosion and heat resistance of several coatings produced by the D-Gun and HVOF processes. From these test results, 50 mass%Alloy625-50 mass%TiO2 cermet coatings were selected and applied to the superheater tubes in a 773 K, 9.8 MPa high efficiency waste-to-energy pilot plant. The coating layer of the final superheater tube disappeared in less than 2000 hours. On the other hand, the coating layer of the secondary superheater tube showed excellent corrosion resistance compared to substrate tubes of 25Cr20Ni-Nb and other corrosion resistance alloys such as Alloy 625.
    This paper describes the laboratory corrosion and thermal shock test results of various D-Gun and HVOF coatings, and examination results of coated tubes exposed 13800 hours in a pilot plant.
    Download PDF (821K)
  • Shozo Ono, Toshikazu Inaba, Takahiro Irie, Hidehiro Kiuchi
    2002 Volume 66 Issue 6 Pages 569-575
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The demand for the highly efficient utilization of the heat generated by waste pyrolysis gasification and melting process is increasing. However, since this process is still under development, the corrosion behavior and characteristics of superheater tubes are not fully understood. Some field corrosion tests were carried out at the model plant to determine the corrosion rate and to clarify the corrosion mechanism of superheater tubes. Thickness losses after practical operation up to 2839 h were measured along with characterization of ashes deposited on the surface of the tubes. It was found that the corrosion loss of SUS310S increased markedly as the metal temperature rise above 500°C. Cl, S, Na, K and Ca were detected in the corrosion scale, and the deposit begins to melt at 504°C. These results indicate that the accelerated corrosion above 500°C is caused by melting of alkaline metal chlorides and sulfates in the deposit. Also, it was confirmed that alloying elements of Cr and Ni affect to reduce high temperature corrosion caused by molten salt.
    Download PDF (1476K)
  • Masaki Uekado, Yuji Kamei, Kenichi Fujii
    2002 Volume 66 Issue 6 Pages 576-582
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    In superheater tubes of high-efficiency waste-to-energy plants, high temperature corrosion may occur when molten salt containing chlorides or sulfates is formed in the ashes deposited on the fireside tube surface. In addition, if residual stress exists in bent or welded parts, high temperature corrosion may be accelerated or crack-like damage may be caused by the presence of the molten salt. In order to investigate the effect of static stress on the high temperature corrosion, crack-like damage tests were conducted in actual refuse ash and synthetic refuse ash at 823 K under static stress applied by the constant load method.
    When buried in synthetic refuse ash containing 20 mass% chlorine under a 0.2% proof stress load condition at 823 K, the SUS304 specimen was fractured by intergranular crack-like damage after 3.6×10 ks. For SUS310J1 and alloy 625, the specimens exhibited no cracking up to 1.08×103 ks. However, the maximum intergranular corrosion depth of SUS310J1 increased as applied stress was increased. Also, as the chlorine concentration in the refuse ash was increased both the maximum intergranular corrosion depth and the maximum corrosion thickness loss tended to increase.
    Download PDF (1409K)
  • Yuuzou Kawahara
    2002 Volume 66 Issue 6 Pages 583-589
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    In order to investigate the melting points and ash deposition behavior of corrosive molten deposits (which are the primary cause of high-temperature corrosion in waste incineration boilers) an electro-chemical monitoring method has been developed and applied to measure the actual melting points and deposition rates at four waste incineration plants.
    As a result, it became apparent that the minimum melting point and the deposition rate could be accurately measured through changes in AC electrode current. It was discovered that the ash deposition rate in operating furnaces increases as gas temperature increases and that the peak in the deposition rate appears as surface temperature increases.
    The peak in the deposition rate is thought to be a result of competing phenomena, namely the increase in the binder effect of molten deposits, the reduction in condensation constituents and the condensation rate with a decrease in ΔT (gas temp.-surface temp. differential).
    These ash deposition phenomena can be explained in terms of the co-effect of the collision of solid and molten particles and condensation from the vapor phase.
    Actual ash deposition behavior in the boiler combustion gas environment corresponded favorably with the data obtained using the new method. Furthermore, it was confirmed that this monitoring method could be used for the accurate assessment of corrosive environments.
    Download PDF (1289K)
  • Yoshiyuki Sato, Hiroya Ishikawa, Motoi Hara
    2002 Volume 66 Issue 6 Pages 590-596
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Hot corrosion of Ni in molten NaCl-KCl-Na2SO4 was investigated at 923 K in atmospheres of 1%HCl and/or 6%H2O in O2-N2. Mass change measurement was accomplished by the thermogravimetric technique using a thermobalance with laser displacement meter. In the atmosphere without HCl, the mass gain of Ni with the molten salt was larger than that without it. In the atmosphere with HCl, the mass gain was quite large, and the mass gain with the molten salt was larger than that without it. With the molten salt, the higher the oxygen potential was, the larger the metal loss of Ni was. Addition of H2O into the atmosphere increased the mass gain of Ni in the atmosphere without HCl, and incorporation of HCl decreased the mass gain. The scale formed on Ni in the molten salt in O2-1%HCl-N2 was NiO and was column-like in shape. The potential-pO2− diagram of Ni in the molten salt in the atmosphere containing HCl was introduced. The diagram showed that the condition of this experiment provides stable dissolution of Ni into Ni2+, and subsequently, NiO formation from Ni2+ and O2− decreases aO2−, which causes change in equilibrium position on the potential-pO2− diagram to Ni2+-stable region again. According to such a mechanism, it was concluded that hot corrosion of Ni in the molten salt in the atmosphere with HCl proceeds in high speed, accompanied by column-like formation of NiO in the salt layer.
    Download PDF (1342K)
  • Long-Xian Ding, Keijiro Nakasa, Masahiko Kato, Takashi Tachiyama
    2002 Volume 66 Issue 6 Pages 597-605
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Mixture of TiB2, Ti and TiC or TiN powder as well as TiB2 and TiC powder were spark- and resistance-sintered to obtain TiB-TiN, TiB-TiC and TiB2-TiC composites. In addition, the plates of these composites were bonded to Ti-6Al-4V alloy substrate by the resistant-sintering. The Vickers hardness and the bending strength of TiB-TiC and TiB-TiN composites reach their maxima at about 20 mol% of TiN or TiC, while those of TiB2-TiC composite take the maxima at about 70 mol% of TiC. The bending strength of the TiB2-70 mol%TiC composite is larger than that of the TiB-20 mol%TiC composite when the sintering temperature is 1973 K. However the bending and adhesion strengths of TiB-20 mol%TiC composite layer bonded on Ti-6Al-4V alloy are larger than those of the TiB2-70 mol%TiC layer when the bonding temperature is 1673 K. The bending strength of the TiB-20 mol%TiC bond layer increases with decreasing ratio of bond layer thickness to substrate thickness, which can be explained by the existence of residual stress introduced during cooling after bonding at high temperature.
    Download PDF (1334K)
  • Atsuo Gyobu, Yoshio Kawamura, Toshio Saburi, Makoto Asai
    2002 Volume 66 Issue 6 Pages 606-613
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The crystallization temperature and composition dependece of morphology of precipitates and precipitates effect on martensitic transformation of sputter-deposited Ti-rich Ti-Ni alloy films were investigated.
    For the investigation by the electron microscopy on precipitates morphology behavior, the deposited amorphous films were crystallized and concurrently aged by holding at various temperatures between 693 K and 823 K. The following schemes were observed depending on Ti-rich Ti-Ni alloy films composition and heat-treatment temperature: (a) Precipitate-free; (b) Plate-like precipitates exist in the B2 phase; (c) Plate-like precipitates and spherical Ti2Ni precipitates coexist in the B2 matrix; (d) Ti2Ni precipitates exist in the B2 matrix; (e) Ti2Ni precipitates with and without orientation relationship to the matrix.
    Then, for investigating composition and crystallization temperature dependence of B2⇔R transformation temperatures the amorphous films were crystallized by holding at various temperatures, 723 K, 773 K and 973 K, for 3.6 ks. For investigation of precipitates effect on the martensitic transformation behavior, the sputter-deposited amorphous films were crystallized and concurrently aged by holding at various temperatures, 695 K and 723 K. The specimens were analyzed with differential scanning calorimetry (DSC) and the following was found. The martensitic transformation behavior changed depending on crystallization temperature and composition. The B2⇔R transformation temperatures of the thin films crystallized at temperatures between 723 K and 773 K were the lowest at Ti-48.5 at%Ni and plate-like precipitates lowered the B2⇔R transformation temperatures.
    The R⇒B19′ transformation temperatures were lowered by distribution of fine Ti2Ni precipitates of Ti-47.0 at%Ni∼Ti-48.5 at%Ni sample crystallized at low temperatures.
    Download PDF (1855K)
  • Tohru Watanabe, Hiroo Sawanobori, Megumi Osada
    2002 Volume 66 Issue 6 Pages 614-620
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Relationships between the crystal size, surface morphology or crystallographic orientation of silver films electrodeposited from an iodine silver bath and the electrodepositing conditions were investigated in detail. In this experiment, in order to know the original structure of the silver films, the electrodeposition was carried out in a bath without any additive, and an amorphous alloy film was used as the substrate. The crystal size of the electrodeposited silver increased with the film thickness and plating temperature, and decreased with the current density. However, it was independent of pH value. The surface roughness was proportional to the silver crystal size. The crystallographic orientation of the silver films var with the film thickness, current density (over voltage), plating temperature and anion species.
    Download PDF (1087K)
  • Hideaki Kuramoto, Kazuhiro Matsugi, Osamu Yanagisawa
    2002 Volume 66 Issue 6 Pages 621-626
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The sintering rate during spark sintering of pure copper powder was measured and analyzed to investigate the sintering mechanism. After the initial stage of spark sintering, where the relative density is smaller than about 0.75∼0.8, relative density is decided only by their temperatures and the sintering rate is decided only by the heating rate at a constant pressure. The mechanism of sintering in this stage is plastic deformation according to this fact and it was suggested that local higher temperature regions by Joule heat generation are present close to the contacts of powder particles. In the next stage, where the relative density is larger than about 0.8 and the heating rate becomes very small, the sintering rate can be represented by the equation including power law creep mechanism.
    Download PDF (457K)
  • Ryuta Onodera, Xu Zhi Quan, Masatoshi Aramaki
    2002 Volume 66 Issue 6 Pages 627-633
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The Portevin-LeChatelier (P-L) effect in Cu-(4-10)at%Al alloys has been investigated in wide ranges of temperature and strain rate. It is shown that the occurrence of serrated flow was primarily determined by the solute concentration, that is, it did not occur in the 4.3 at%Al alloy and occurred strongly in the 10.1 at%Al alloy. It occurred weakly in the 7.4 at%Al alloy, which suggests that the Al concentration of 7 at% is the critical one for the P-L effect. It is also shown that the prediction by the Cottrell theory is inconsistent with the experimental result in the point of effects of solute concentration and strain rate on the occurrence of serrated flow. The formation of short range ordered region is proposed as a reasonable cause of the P-L effect in the alloy.
    Download PDF (413K)
  • Nobuyuki Mori, Keisaku Ogi
    2002 Volume 66 Issue 6 Pages 634-642
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The numerical and analytical studies of solidification process of faceted 123(YBa2Cu3O7−X) crystals from liquid +211(Y2BaCuO5) phases are essential to clarify the solidification mechanism and improve the properties of YBCO. Two-dimensional numerical simulations of faceted peritectic growth of 123 crystal were performed by considering growth of 123 crystal, melting of 211 particles in the liquid, and solute diffusion in the liquid. The growth rate (Vk) of 123 crystal was approximated by: Vk=ak·(ΔTkTp)2, where ak: kinetic growth coefficient, ak=ak0·[(tanξ⁄β)·tanh(β⁄tanξ)·{1⁄cos(π⁄4)−1}+1], ak0: growth constant, β: constant, ξ: angle between the interface and facet plane, and ΔTk: kinetic undercooling of faceted interface, Tp: peritectic temperature. Solute distributions in the liquid during the 123 growth were calculated with FDM, and the distributions of residual 211 particles and liquid pools in the faceted 123 crystals were simulated from the experimentally obtained log-normal distribution of 211 particles in the YBCO melt. The calculated results agreed well with the experimental ones. Further, the transition of macrostructures from columnar to equiaxed 123 crystals in unidirectionally solidified YBCO was also studied experimentally and analytically. The critical transition condition (:a function of growth rate (R) and temperature gradient(G)) were calculated by equations obtained from nucleation and growth theories, and compared with experimental results.
    Download PDF (931K)
  • Toshifumi Hirasaki, Atsushi Nishikata, Tooru Tsuru
    2002 Volume 66 Issue 6 Pages 643-648
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The influence of dissolved zinc ion on the anodic dissolution of iron was investigated by potentiodynamic measurement and channel flow electrodes. In the polarization curves of iron, the anodic current around the immersion potential decreased with increase of zinc ion concentration in acidic solution, but increased in neutral solution. It is considered that the anodic dissolution of iron in acidic solution containing zinc ion was inhibited by the adsorption species onto the iron surface. In neutral solution containing zinc ion, the anodic dissolution of iron was accelerated by decrease in pH near the electrode caused by hydrolysis reaction of dissolved zinc ion. In the case of bare iron on which air formed oxide film was removed, the anodic dissolution of iron is inhibited by the presence of zinc ion in both acidic and neutral solution.
    Download PDF (563K)
  • Katsuhiko Asami, Michio Kikuchi
    2002 Volume 66 Issue 6 Pages 649-656
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Several weathering steels and a plain carbon steel exposed to atmosphere for 17 years at Yokkaichi (at a coastal and industrial region) and Mikuni Pass (at a rural region) in Japan were analyzed and compared to find effects of environments on the formed rusts. Specimens were examined with electron probe microanalysis (EPMA), X-ray diffraction (XRD) and transmission electron microscope (TEM). Their cross-sections were also analyzed by EPMA. XRD detected mainly α-FeOOH as major rust constituent and β-FeOOH and γ-FeOOH as minor ones in the surface region. The concentration of β-FeOOH was especially high on the skyward surface of all the specimens irrespective of steel composition. EPMA results showed that Si, Na, S were abundant on the skyward surface. In the cross-section, alloying elements Cu and Cr were enriched in the inner layer of rust as well as Si, while P and Ni did not show any characteristic distribution. TEM examination of cross-section of rusts showed that α-FeOOH was also main constituent of the rust. The β-FeOOH showed no special distribution feature in the main part of rust except in the very surface region. Amorphous rust judged from electron diffraction and Fe3O4 distributed mainly near the interface between steel and rust layer. The γ-FeOOH was contained much more in rust on plain carbon steel than weathering steels. A quantity ratio α⁄γ*, that is, the ratio of α-FeOOH to the sum of β-FeOOH, γ-FeOOH and magnetite, is >1 for a weathering steel, and <1 for a mild steel. The Si in the inner layer was suggested in the form of SiO44− state.
    Download PDF (1121K)
  • Susumu Kumagai, Yasuhide Shindo, Katsumi Horiguchi, Daiki Shinohe
    2002 Volume 66 Issue 6 Pages 657-661
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Tension and in-plane shear tests have been carried out to measure the in-plane mechanical properties of T800H/3633 CFRP woven laminates at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K). Tensile and shear tests were conducted according to the following JIS standard procedures: JIS K 7073 for tensile tests, and JIS K 7079 for shear tests. The specimen geometry utilized in the determination of the fiber-aligned strength included a dog-boned shape and wedge tabs. A two-dimensional finite element analysis was also used to study the stress distributions within the dog-bone shaped specimens and to interpret the experimental measurements.
    Download PDF (630K)
  • Shintaro Ishiyama, Yasushi Muto
    2002 Volume 66 Issue 6 Pages 662-669
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    A turbine disk model, which uses a C/C composite material to lighten the turbo machinery rotor for a trial HTGR-GT system, was fabricated to try to achieve a circumferential speed of up to 500 m/s during the spin test. In the present study, the design and production of the largest turbine disk model (the outside diameter×inside diameter×thickness=φ450 mm×φ250 mm×t40 mm) in the world has been implemented by high strength carbon fiber reinforcement in the hoop, radius and thickness directions and SiC/I-CVI processing. As a result of the spin tests, the following conclusions were obtained.
    (1) SiC layer of 2.5-20 μm in thickness was achieved by SiC/I-VCI processing in the C/C composite disk model with 40 vol%, 10 vol% and 4 vol% carbon fiber in the hoop, radial and thickness directions.
    (2) SiC layer formation in the disk model structure shows reinforcement and prevention against delamination of carbon fiber in the disk model at spin test.
    (3) 500 m/s circumferential speed was achieved by spin test of SiC/I-CVI C/C composite disk model. This value is the fastest speed recorded by two or three dimensional reinforcement C/C composites.
    (4) Fracture of the disk model was induced by crack initiation and propagation from inside to outside wall surface of the disk model, observed by a direct crack propagation observation technique.
    Download PDF (1286K)
  • Masami Taguchi, Hiroshi Sugita
    2002 Volume 66 Issue 6 Pages 670-675
    Published: 2002
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    In order to investigate the discharge/charge process of the active materials for the positive electrode in the lead-acid battery, a PbO2 thin film was deposited on a piezoelectric quartz crystal by reactive sputtering, and then the in situ observations of the mass change in the PbO2 electrode were carried out using the electrochemical QCM technique. The PbO2 thin film produced by sputtering a pure Pb target in an oxygen plasma was identified as a mixture of α-PbO2 and β-PbO2. The discharge process by a very low current suggested that the reaction of PbO2→PbSO4 proceeded first and then the reactions such as PbO2→PbO, PbO→Pb and PbSO4→Pb occurred one after another. During the potentiostatic discharge/charge process, most of the discharge reaction of PbO2→PbSO4 was completed at the beginning of the process, while the charge reaction of PbSO4→PbO2 slowly proceeded. The conversion ratio of the PbSO4 back to the original PbO2 during charge was estimated to be only 52% or so based on the mass change. Right after the start of both the discharge and charge, the mass decreases in sharp intervals as the result of the dissolution-precipitation mechanism were confirmed by the electrochemical QCM technique for the first time. The repetition of the discharge/charge increased the ratio of β-PbO2 to α-PbO2 in the charged product. Moreover, there were PbSO4 crystals of various sizes on the PbO2 surface after discharge, and the small crystals in the lower part dissolved earlier than the large ones to be transformed into the PbO2 particles of tens of nanometers during the charge. These results suggest that the refinement of the PbSO4 crystals during discharge is an important factor to improve the charge of the active materials for the positive electrode.
    Download PDF (808K)
feedback
Top