Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Volume 63 , Issue 5
Showing 1-32 articles out of 32 articles from the selected issue
  • Yoshimasa AOYAMA
    1977 Volume 63 Issue 5 Pages 561-573
    Published: April 01, 1977
    Released: February 22, 2010
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  • Yoshihiro HISAMATSU
    1977 Volume 63 Issue 5 Pages 574-584
    Published: April 01, 1977
    Released: February 22, 2010
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  • Yoshihiro HISAMATSU, Hiroyuki OGAWA
    1977 Volume 63 Issue 5 Pages 585-597
    Published: April 01, 1977
    Released: February 22, 2010
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  • Iwao MATSUSHIMA, Jun-ichi SAKAI
    1977 Volume 63 Issue 5 Pages 598-604
    Published: April 01, 1977
    Released: February 22, 2010
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    The mechanism of crevice corrosion in stainless steels has been studied using an electrochemical technique. Experiments were conducted based on the idea that the rate of crevice corrosion could be determined by combining the crevice potential and the polarization curve in low pH, high Cl- solutions simulating the solution within crevice. The crevice potential determined by inserting a luggin capillary into a crevice made by coupling two stainless steel Plates is in the range of -250 to -350 mV vs SCE. The rate of dissolution indicated by the polarization curve in 5M NaCl, pH 2, and the measured crevice potential is in good agreement with the corrosion rate obtained by the immersion test of the crevice specimen in neutral 3.5% NaCl solution. It is demonstrated by direct measurements of the crevice specimen and by supplementary experiments using a simulated crevice corrosion system that the electrochemical cell controlling crevice corrosion can be described quantitatively in terms of gotentials inside and outside of the crevice, solution resistance in the crevice and the polarization behavior in the crevice solution. The application of the results to crevice corrosion testing is also discussed.
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  • Hiroyuki OCAWA, Isao ITOH, Michio NAKADA, Yuzo HOSOI, Hideya OKADA
    1977 Volume 63 Issue 5 Pages 605-613
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    A quantitative analysis has been made on the initiation of crevice corrosion on the following assumption: (1) The pH in crevice is uniquely determined by the total charge passed as passive current, and (2) the crevice pH decreases to depassivation pH at which active dissolution, crevice corrosion, initiates.
    The obtained results are summarized in the followings: (1) The chloride-ion concentration and pH in the artificial pit are closely related to the total charge passed as passive current, and (2) depassivation pH is mainly dependent on dissolved oxygen concentration and alloying elements expressed as (Cr%+3Mo%+0.5Ni%).
    The quantitative method for the estimation of the incubation time for crevice corrosion is proposed on the basis of passive current density and depassivation pH. A reasonable correlation is found between the incubation time based on the proposed method and that measured for SUS304 and SUS316 stainless steels in sea-water.
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  • Toshiro ADACHI, Tuguyasu YOSHII, Takahiko MAEKITA
    1977 Volume 63 Issue 5 Pages 614-621
    Published: April 01, 1977
    Released: February 22, 2010
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    The change of pH in corroding crevices has been investigated. Crevice specimens were immersed in NaCl solutions, and the pH and the Cl- ion concentration in crevices were determined. The potential inside the crevice was also measured with a capillary inserted into the crevice.
    The results show that the pH in crevice becomes lower with development of crevice corrosion. The stationary pH of the SUS 304 crevice is 2.5 to 4. The enrichment ratio of the Cl- ion in the SUS 304 crevice is increased, as the concentration of the Cl- ion in the test solution or the crevice volume is decreased. Judging from the pH in crevice and the potential inside crevice, it seems that active state is attained in the SUS 304 crevice. The steels which contain Mo more than 2% have a tendency to show lower pH in crevices in comparison with low Mo steels.
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  • Motohiko TAKEDA, Keiichi YOSHIOKA, Yutaka ONO, Nobuo OHASHI
    1977 Volume 63 Issue 5 Pages 622-630
    Published: April 01, 1977
    Released: February 22, 2010
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    To clarify the cause of intergranular corrosion of 17% Cr fbrritic stainless steels, precipitation of chromium carbides and nitrides at grain boundaries was studied by electricalresistivity measurement and electron microscopic observation on the steels having various amounts of carbon and nitrogen.
    On the quenched and isochronously annealed specimens, precipitation was found at two stages for chromium carbides, (Fe, Cr) 7C3 at 550°-650°C and Cr23C6 at above 700°C, and also at two stages for chromium nitrides, the one of not identified structure at 400°-550°C and Cr2N at 650°-750°C.
    Intergranular corrosion susceptibility was remarkably raised by the precipitation of (Fe, Cr) 7C3 at 550°-600°C and “unknown” nitride at 400°-550°C.
    Chromium depletion zone along grain boundaries formed by the very rapid precipitation of these special types of carbide and nitride at the intermediate temperatures around 550°C was indicated as the most probable reason for intergranular corrosion.
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  • Takashi OKAZAKI, Masanori MIYOSHI, Hideo ABO, Taku HIRAI
    1977 Volume 63 Issue 5 Pages 631-640
    Published: April 01, 1977
    Released: February 22, 2010
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    Intergranular corrosion at weld zone of 17% Cr steel was investigated. Commercially produced 17% Crsteel (SUS 430) contains usually about 0.06-0.08% C+N and is fairly resistant to intergranular corrosion at weld zone inactual services where the environment is not severe. On the other hand, 17% Cr steel containing 0.01-0.06% C+N, is quite susceptible to intergranular corrosion at weld zone in mild corrosion environments such as tap water. The experimental results indicate that this can be attributed to the decrease of martensite at weld zone. The martensite (austenite at high temperature) acts as the absorber of C and N, and prevents the deposition of Cr-carbide or Cr-nitride at grain boundaries on welding. Therefore, 17% Cr steel containing martensite at weld zone is more resistant to intergranular corrosion than 17% Cr steel, the structure of which is fully ferritic at weld zone. The amounts of Ti necessary to prevent intergranular corrosion at weld zone was also determined. Electrocbemical measurements gave results that agreed with the immersion test.
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  • Masao ONOYAMA, Masanobu TSUJI, Susumu TAKEMURA
    1977 Volume 63 Issue 5 Pages 641-658
    Published: April 01, 1977
    Released: February 22, 2010
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    A study has been made of ferritic stainless steels, which are not susceptible to stress corrosion cracking and comparable in corrosion resistance to type 304 steel in relatively mild environments. Cold rolled sheets of various compositions are prepared in the laboratory from ingots made by vacuum induction melting and their resistance to pitting, general corrosion, and stress corrosion cracking are examined. Good corrosion resistance is obtained by 19% Cr, 2% Mo, and Ti and/or Nb equivalent to more than 16 times of the C+N content and maintaining the interstital elements, i. e., C and N as low as possible.
    While Ti improves the ductility of the weld, the element causes the surface defects such as Ti-streak on cold rolled strip, when a sufficient amount of Ti for stabilization is added. Therefore, combined additions of Ti and Nb are preferable.
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  • Kazuo HOSHINO
    1977 Volume 63 Issue 5 Pages 659-667
    Published: April 01, 1977
    Released: February 22, 2010
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    Effects of chemical composition on season cracking, which occurs in metastable austenitic stainless steel after deep drawing, were studied. The main results obtained in this study are as follows.
    1) The sensitivity to season cracking is not determined only by the volume fraction of strain-induced martensite. It is affected by chemical composition. The effects of chemical composition on hardening martensite and injuring the toughness of it are most related to the sensitivity to season cracking.
    2) This relation is introduced by the behaviors of K/σ0.2 vs. σ0.2. which are measured in 60% cold rolled materials.
    3) Carbon and phosphorus are very harmfull and nitrogen is harmless compared with carbon.
    4) Addition of silicon and aluminum is of use in preventing season cracking.
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  • Shigeto YAMAGUCHI
    1977 Volume 63 Issue 5 Pages 668-673
    Published: April 01, 1977
    Released: February 22, 2010
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    A mirror surface of austenitic stainless steel was finished by polishing with an aqueous suspension of alumina. During the colloid chemical polishing, the oxide particles were evenly embedded in the substrate, and at the same time the surface layer underwent a martesitic transformation.
    The solid state reaction that took place between the abrasive oxide particles and the alloy substrate was promoted in virtue of the magneto-catalytic Hedvall effect, since the martensitic transformation concerned gave rise to a ferromagnetic and distorted lattice structure.
    The lustrous mirror surface that was obtained proved to be dielectric, ferromagnetic and corrosionresistant so that it was susceptible to the electrooptic effect, e. g. to Faraday and Kerr effect.
    The crystallographic, magnetic, and dielectric analyses were carried out in terms of electron diffraction reflection, and it was demonstrated that this procedure could serve as a quality testing of austenitic steel.
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  • Taishi MOROISHI, Hisao FUJIKAWA, Hirofumi MAKIURA
    1977 Volume 63 Issue 5 Pages 674-680
    Published: April 01, 1977
    Released: February 22, 2010
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    The effect of zirconium alloying on the oxidation resistance of 15% to 18% chromium steels has been investigated by means of isothermal heating at the temperatures up to 1000°C. Alloying of zirconium the amount of which exceeds its stoichiometric equivalent to the total amount of carbon and nitrogen in steels is found to improve the oxidation resistance of chromium steels. Electron probe microanalysis of the scales formed on the zirconium containing steels can detect no zirconium in the scales and shows prominent chromium enrichment in the inner scales. Extraction analysis of precipitates in the steels after heating up to 1 100°C reveals the zirconium carbonitrides to be stable up to 1000°C. The stable precipitates prevent the steels from grain growth when heated up to 1000°C. The beneficial effect of zirconium on the oxidation resistance of chromium steels is considered to be attribute to stable zirconium carbonitride precipitates which prevent the steels from release of carbon and grain growth in the course of oxidation at temperatures up to 1000°C.
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  • Takashi SUZUKI, Norio KAWABATA
    1977 Volume 63 Issue 5 Pages 681-687
    Published: April 01, 1977
    Released: February 22, 2010
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    In recent years there has been a need for materials that sustain satisfactorily at higher temperature in automobile exaust emission control systems. In order to select the materials for such cyclic services, scaling resistance of a number of commercial heat resisting steels have been investigated for long period under cyclic heating in air between 800 and 1200°C.
    Oxidation behavior is dependent upon both microstructure and chemical composition of alloys. The ferritic alloys exhibit better resistance to scaling than the austenitic alloys. Fe-Cr-Al alloys show excellent oxidation resistance at high temperature, but deformation of specimen occurs. Austenitic alloys show a general trend of improved resistance to scaling with increasing Cr, Ni and Si contents. 18-8 stainless steels bearing a small amount of Ti or Nb plus Ta show also improved resistnance.
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  • Yukishige FUKASE, Rikio NEMOTO
    1977 Volume 63 Issue 5 Pages 688-699
    Published: April 01, 1977
    Released: February 22, 2010
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    An austenitic stainless steel with high silicon, 13Ni-18Cr-3.5Si alloy has recently been developed and recongnized as a new alloy resistant to the high temperature oxidation. This alloy has been adopted for a thermal reactor in the automobile field because it has an excellent resistance to oxidation and both the weldability and formability are superior to those of SUS310S. The oxidation mechanism of 13Ni-18Cr-3.5Si alloy, however, is not so clear as those of 35Ni-20Cr and 80Ni-20Cr alloys with high silicon.
    In order to clarify the oxidation mechanism and the effect of strong deoxidation process, a cyclic oxidation test at 1000°C in air was carried out on 13Ni-18Cr-3.5Si alloys made through deoxidation process.
    The surface morphology, microstructure, and composition of oxide were examined by means of optical microscopy, X-ray diffraction, scanning electron microscopy, and electron probe microanalysis.
    No internal oxide was detected by optical microscopy or electron probe microanalysis of sections, while the adherence of the surface oxide was retained in 13Ni-18Cr-3.5Si alloy. The formation of a very thin amorphous SiO2 film was detected beneath innermost oxide Cr2O3 by scanning electron microscopy and electron probe microanalysis of the back of oxide chemically stripped from 13Ni-18Cr-3.5Si alloy. It was assumed that this thin SiO2 film contributed to the improvement of the resistance to oxidation.
    Protective and mechanical properties of the SiO2 film were markedly affected by the strong deoxidation process. The highly convoluted oxide/alloy interface was observed on 13Ni-18Cr-3.5Si alloy made by strong deoxidation with rare earth metals. The good oxide adherence was attributed to the improvement in the plasticity of thin SiO2 film formed at oxide/alloy interface by rare earth element as an inpurity. An optimum combination of Si addition and strong deoxidation process was concluded to further improve the resistance to oxidation at high temperatures.
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  • Yuji SHOJI, Shun-ichiro AKIYAMA, Masaru KISAICHI, Kyosuke NAGATOSHI, H ...
    1977 Volume 63 Issue 5 Pages 700-714
    Published: April 01, 1977
    Released: February 22, 2010
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    The oxidation behavior of Fe-18Cr-10Ni and Fe-20Cr-10Ni steels containing 1 to 3%Si and Fe-20Cr-10Ni-2.5Si steels containing rare earth elements up to 0.22% has been investigated under continuous and cyclic oxidation conditions in air in a temperature range from 800 to 1100°C by a thermogravimetric method, metallography, X-ray diffraction, and EPMA.
    In both the continuous and cyclic oxidation conditions, the weight gain curves have steps of the protective stage breakthrough stage (spalling stage in the cyclic condition), and heating stage. The increase of silicon and chromium contents improves the oxidation resistance.
    The marked improvement of scale adherence is attained by the addition of rare earth elements, which delay the beginning of the spalling in the cyclic oxidation.
    With the addition of rare earth elements, the growth of chromium depleted zone is restrained, consequently the formation of the stratified oxide which causes the spalling in cyclic oxidation is depressed.
    In addition, the network of SiO2 grows deeply into the substrate and prevents the propagation of the stratified oxide along chromium depleted zone, therefore the scale adherence is improved remarkably.
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  • Shozo IIZUMI, Masayuki KINUGASA, Tokio FUJIOKA
    1977 Volume 63 Issue 5 Pages 715-723
    Published: April 01, 1977
    Released: February 22, 2010
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    Recently, austenitic stainless steels containing high Si are considered as material to be used for automobile exhaust-emission-control systems. A study has been made of the effects of rare earth elements and Ca upon the oxidation behavior of 19%Cr-13%Ni-3%Si-Fe system steel in air in the temperature range from 1000 to 1200°C.
    The addition of suitable amount of rare earth elements improved markedly the scaling resistance and the spalling resistance up to 1100°C, but did not improve the scaling resistance at 1200°C. On the contrary, the addition of Ca improved remarkably the scaling resistance up to 1200°C and spalling resistance at 1000°C, but did not improve the spalling resistance at 1100°C so much. The complex addition of suitable amount of rare earth elements and Ca was very effective for both the scaling resistance and the spalling resistance up to high temperature.
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  • Satoshi KADO, Taketomo YAMAZAKI, Mikio YAMANAKA, Kotaro YOSHIDA, Katsu ...
    1977 Volume 63 Issue 5 Pages 724-735
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    The development of Cr-Al steels for automobile emission control devices has been really desired from both the standpoint of low cost and economy of nickel resource. Cr-Al steels, however, are poor in formability and weldability, and moreover they sometimes suffer from such abnormal oxidation that oxidation proceeds locally in oxidizing atmospheres. Especially, the abnormal oxidation proceeds in a more accelerated from in exhaust gas than in air.
    In this study, the effects of alloying elements, Cr, Al and Ti, on the resistance to abnormal oxidation, formability and also weldability of Cr-Al steels were investigated.
    Consequently the addition of 0.3% titanium to Fe-22% Cr-2.4% Al-base alloy containing low C and low N was found to improve the resistance to abnormal oxidation in exhaust gas, formability and weldability.
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  • Satoshi KADO, Taketomo YAMAZAKI, Mikio YAMANAKA, Kotaro YOSHIDA, Katsu ...
    1977 Volume 63 Issue 5 Pages 736-747
    Published: April 01, 1977
    Released: February 22, 2010
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    Recently, various emission control devices for automobile suh as thermal reactors and catalytic convertors have been designed and put in practical use for anti-pollution purposes.
    In this study, to offer the necessary data to decide the most suitable materials for these devices, oxidation tests for comparatively good oxidation-resistant stainless steels have been carried out in the atmospheres of exhaust gas from automobile engine at high temperatures, and the mechanism of high temperature corrosion occuring on the materials has been studied.
    In the exhaust gas, the oxidation of materials takes place in a more accelerated form than in air.
    By calculating the sulfer potential of the exhaust gas consisting of CO-CO2-COS-SO2-S2-O2 system, it is concluded that the oxidation of the materials by CO2, H2O, and O2 in the exhaust gas at high temperatures is accelerated by sulfer, by the formation of sulfer compounds such as iron, chromium, or nickel sulfied between the oxide scale and the base metal.
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  • Teruo TANAKA, Shozo IIZUMI, Masayuki KINUGASA, Tokio FUJIOKA
    1977 Volume 63 Issue 5 Pages 748-758
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    Thermal fatigue properties of a number of austenitic heat resisting steels have been studied by using a testing equipment that can either strain and temperature cyclings independently.
    The microstructural and fractographical studies have also made. The results are as follows:
    (1) Under 200/1000°C temperature cycling, R2 (19Cr-15Ni-3Si-Al) has slightly better thermal fatigue life (Nf) than SUS310S and R1 (19Cr-13Ni-3Si-Nb). Under 200/800°C and 200/700°C temperature cyclings, the order of steels in Nf changes with the change in total strain range (Δ∈t). That is, SUS304 has a better thermal fatigue life than the others when Δ∈t is in a higher value, but than the others when Δ∈t is a lower level.
    (2) Under 200/1000°C temperature cycling, the ductility of steels principally contributes to Nf. On the other hand under 200/800°C and 200/700°C temperature cyclings, the ductility of steels greatly contributes to Nf when Δ∈t is in a higher level, and the strength of steels during thermal fatigue test greatly contributes to Nf when Δ∈t is in a lower value.
    (3) The cracks in the steels tested under 200/800°C and 200/700°C temperature cyclings are generally transgranular, and the fracture surfaces reveal striations, In SUS310S, however, which has much precipitation near the grain boundary, the most cracks propagate along the grain boundary. Thus, it is understood that the structural change during thermal fatigue test has a large influence on the thermal fatigue properties.
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  • Tadashi SAWATANI, Shigeru MINAMINO, Minori YAMAGUCHI
    1977 Volume 63 Issue 5 Pages 759-771
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    17%Cr stainless steel containing Al has better deep drawability than SUS430 does, The followings have been found in this investigation.
    (1) The mechanical properties and formability of 17%Cr stainless steel are effectively improved by the addition of Al more than 6 times N content and less than 0.1% in weight.
    (2) The increase of Al/N ratio improves the r value in cold rolled and annealed steel sheet.
    (3) Results of texture examination show that the increase of Al/N ratio does not change the cold rolled texture but intensifies {111} and {112} and surpresses {110} and slighdy {001} components in recrystallized texture.
    (4) The poor bending workability after cold rolling due to Al addition originates mainly in the precipitated AlN. To improve the bendability, the following conditions are especially required (%Al as AlN) +0.3× (%C) <0.04 and N≤0.01%.
    On the basis of these results, the 17%Cr stainless steel containing Al which has superior deep drawability and good bending workability after cold rolling has been successfully manufactured.
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  • Kiyohiko NOHARA, Yutaka ONO, Nobuo OHASHI
    1977 Volume 63 Issue 5 Pages 772-782
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    Composition and grain size dependencies of Md30, the parameter proposed by Angel for indicating austenite stability during deformation in metastable austenitic Fe-Ni-Cr stainless steels, were examined.
    The measurement of Md30 by changing composition, C, N, Si, Mn, Ni, Cr, and others, give the following empirical equation: Md30 (C) =551-462 (C%+N%) -9.2Si%-8.1Mn%-13.7Cr%-29.0 (Ni%+Cu%) -18.5Mo% -68.0Nb%. A great coefficient for Ni in this equation is quite different from that in the Angel's equation. With decreasing grain size of austenite, the amount of strain-induced martensite decreases, and Md30 is lowered. Consequently, MdGS30 which is Md30 modified by the grain size effect, can be expressed as MdGS30=Md30 -1.42 (ν-8.0); where ν is ASTM grain size number.
    The proof stress drops during deformation at lower temperatures because of the inducement of martensite at a small strain. This phenomenon easily occurs in the specimen with finer grain size. On the stress-strain curve the serrated region can be easily found in the deformation of the specimen with finer grain size. The amplitude of serration becomes too small to be observed in such cases as the specimen with coarser grain size, lower deformation temperature and stabilization of austenitic phase, even though a lot of martensite is induced.
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  • Toru FURUKAWA, Shizuyo ONUMA
    1977 Volume 63 Issue 5 Pages 783-793
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    In order to make clear the roles of Al and C in 17Cr-7Ni stainless steel, the microstructural features, Ms temperature, and mechanical properties were investigated for the steels containing variable amounts of Al and C. The results obtained are as follows:
    (1) The quantity of δ-ferrite in matrix increased with the increase of Al content, or the decrease of C content. No δ-ferrite is observed in the range of Al content less than about 0.7%, but the phase of δ-ferrite is nearly 10 and 50% in matrix for steels containing about 1 and 2% Al, respectively. Furthermore, for the steels containing about 0.01 and 0.07% C, the phase of δ-ferrite exists in 45 and 10% in matrix, respectively. And also when C content in steel is more than 1%, the δ-ferrite can not be observed.
    (2) According to our experiments, it seems that the Ms temperature is raised in rate of 20°C per 1% Al, and is dropped down about 14°C per 0.01% C in content.
    (3) It is confirmed that the microstructural features and the Ms temperature are affected sensitively with Al and C content.
    (4) The best mechanical properties is obtained for the steel containing about 1.2% Al and 0.07% C. Also it can be recognized that the age hardenability are increased with the increase of Al content, and with the decrease of C content.
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  • Masakuni FUJIKURA, Teruhiko SOH
    1977 Volume 63 Issue 5 Pages 794-803
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    A study was made of the effects of Ni on the deformation-induced martensitic transformation and mechanical properties of 18Cr-Ni, 18Cr-2Mo-Ni, 18Cr-4Mn-Ni, and 18Cr-5Mn-0.25N-Ni austenitic stainless steels.
    The deformation-induced martensitic transformation was discussed in terms of stacking fault energy and chemical free energy difference (ΔGα′→γ). Furthermore, the influence of microstructure of austenitic stainless cast steels on mechanical properties was investigated.
    The results obtained are as follows:
    1) With increasing Ni contents, the mode of deformation-induced martensitic transformation changes from the reaction of γ→∈′→α′ to the one of γ→α′.
    2) The amount of ∈′ martensite of speciments strained to 20% at -180°C shows a peak value at a particular Ni content which is characteristic of each series.
    3) 0.2% proof stress varies with the test temperature and Nicontent. With decreasing Ni content of metastable austenite, 0.2% proof stress lowers and it is supposed that this cause is due to γ→∈′ martensitic transformation.
    4) Martensite transformation during Charpy test gives no effect on the impact value at -196°C, and it depends only on the toughness of austenite at the test temperature.
    5) δ ferrite exists in cast steels because of the segregations and transforms to σphase. Charpy impact value lowers as ferrite percentage increases in 18Cr-Ni cast steels and so dose σphase in 18Cr-2Mo-Ni cast steels.
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  • Akihiko HOSHINO, Masao KANAO, Keishi NAKANO
    1977 Volume 63 Issue 5 Pages 804-811
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    The effect of heat treatment on the mechanical properties of Fe-25Cr-6Ni alloy has been investigated, and the results are summarized as follows.
    (1) In case of aging at 475-525°C, the tensile strength and 0.2% proof srtess increase continuously with aging time owing to the precipitation of Cr-rich phase in ferrite matrix. In spite of the decrease in elongation, the reduction of area shows an approximately constant value of 60-70%.
    (2) Heating at 650-800°C produces the α-γ transformation and proof stress decreases with the increase of γ content. The tensile strength that is affected by work hardening of γ phase during the deformation does not vary in parallel with the proof stress.
    (3) Charpy impact value decreases with aging time at 475-525°C. The testing temperature dependence of the Charpy impact valus is based on the raise in the transition temperature due to the 475°C embrittlement.
    (4) The prior α-γ transformation that produces an increase in γ content and an increase of Cr concentration in α phase leads to the reduction of susceptibility for 475°C embrittlement.
    (5) It is observed that σ phase in two-phase stainless steel is formed by decomposition of high Cr ferrite phase into σ+γ, independently of Cr carbide.
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  • Nobuo OHASHI, Yutaka ONO, Kiyohiko NOHARA
    1977 Volume 63 Issue 5 Pages 812-823
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
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  • Motohiko ARAKAWA, Hidehiko SUMITOMO
    1977 Volume 63 Issue 5 Pages 824-831
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    A study has been made mainly of the effects of dry lubricant films on the press formability and the galling of austenitic and ferritic stainless steel sheets. The results obtained are summerized as follows:
    (1) The galling occurs more easily on stainless steel as compared with carbon steel, but it is possible to suppress the galling by using dry lubricant film.
    (2) The deformability of sheet is remarkably improved by film, therefore ferritic stainless steel sheet with the film has rather good press formability than 18-8 steel sheet with conventional high lubricating oil.
    (3) In round-bottomed punch stretching (punch dia. 97mm, die dia. 100mm), the effect of the film is in the same as (2) above, and the change of strain in thickness in the stretching with the film is similar to it in hydraulic bulging, but in Erichsen test it's effect is small. It must be noted that dimensions of punch and die have a large effect on the thickness changes in the stretching.
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  • Tadashi SAWATANI, Kunihiko SHIMIZU, Tadashi NAKAYAMA, Takashi HIRAI
    1977 Volume 63 Issue 5 Pages 832-842
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    Press formability of Ti-stabilized low C, N-17% Cr stainless steel is evaluated by various model forming experiments in comparison with SUS430 and SUS304.
    Ti-stabilized steel is superior to SUS430 but inferior to SUS304 in ductility, deep drawability, and secondary formability. Ti-stabilized steel achieves deep drawability almost equal to that of SUS304 when a new ester type synthetic lubricant is applied.
    Ti-stabilized steel is very supeior to SUS430 in ridging but this steel is not immune from surface wrinkle after pressing because there is a tendency of easy grain coarsning. The surface wrinkle appears as a result of simultaneous occurrence of ridging and orange peal and increases linearlly as the equivalent strain of the deformed part increases. The tendency is improved by a single cold rolling process with high cold reduction.
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  • Tadashi SAWATANI, Kunihiko SHIMIZU, Tadashi NAKAYAMA, Masanori MIYOSHI
    1977 Volume 63 Issue 5 Pages 843-854
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    The effect of mill processing variables on the r-value and texture of Ti-stabilized low C, N-17% Cr stainless steel has been investigated. The results obtained are as follows;
    (1) The r-value in cold rolled and annealed steel sheet is very effectively improved by Ti addition of 0.2-0.3 weight percent but the excessive addition should be avoided because the recrystallization temperature is shifted to a higher range.
    (2) The optimum r-value is obtained by the following conditions: Finishing temperature of hot rolling is low. Hot rolled sheet is annealed at 900°C, with a rapid heating rate and a cooling ra te as fast as air cooling. Cold reduction is more than 80% and in case of two stage cold rolling and annealing process the distribution between 1st and 2nd reduction is 40% to 60%. Finally, intermediate of final annealing temperature is 850°C.
    (3) When favorable fine carbo-nitride precipitates are formed in hot rolled sheet before cold rolling by conforming the above processing conditions, these precipitates seem to develop strong {112} <110> deformation texture in high cold reduction and supress {110} <001> and develop strong {554} <225> component in the recrystallized texture, resulting in annealed products with very high r-values.
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  • Keijirou SUZUKI, Shozaburou ASAMI, Kazuyoshi SUZUKI
    1977 Volume 63 Issue 5 Pages 855-864
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    The origin of ridging phenomenon in 18% Cr ferritic stainless steel sheet was studied and the following results were obtained.
    (1) Macroscopic stripe pattern which was composed of many dark and bright microscopic stripes running along the rolling direction of sheet was observed on the surface of sheet when it was severely etched.
    (2) Macroscopic and microscopic stripes corresponded with large and small undulations of ridging, respectively, which was appeared after stretching of sheet.
    (3) Line analysis with EPMA across the dark and bright zones in stripe pattern showed clear segregation of chromium and carbon.
    (4) This segregation was inherited from the two-phase structuse, austenite and ferrite, in hot rolled sheet and was hold even in cold rolled and annealed sheet. Each segregation zone was extended by cold rolling and made a stripe pattern on the surface of sheet.
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  • Setsuo KAWASHIMA, Ryoichi KESSOKU, Satoru KANEKO, Kenji HARADA
    1977 Volume 63 Issue 5 Pages 865-871
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    The effects of Cr, Ni, and C contents on the press formability and mechanical properties of austenitic stainless steels containing Cu were investigated.
    The main results obtained are as follows.
    (1) The addition of Cu to austenitic stainless steels results in low work hardening, good drawability, and good corrosion resistance to acid environments.
    (2) The press formability of 13-18% Cr-6-9% Ni-2% Cu steels is strongly affected by the degree of austenite stability, and the optimum composition for the deep drawability and that for the stretch formability do not coincide with each other.
    The more unstable the austenite when formed, the better the deep drawability in the range of containing no martensite as annealed. The stretch formability, however, becomes the maximum when the austenite is a little unstable.
    (3) Delayed cracking of deep drawn cups does not occur at C content up to about 0.03%.
    (4) 16% Cr-7% Ni-2% Cu (low-C) steel has excellent press formability.
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  • Harumasa NAKAMURA
    1977 Volume 63 Issue 5 Pages 872-882
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
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  • Satoshi KADO, Taketomo YAMAZAKI, Isamu YAMAUCHI, Katuhiko YABE
    1977 Volume 63 Issue 5 Pages 883-893
    Published: April 01, 1977
    Released: February 22, 2010
    JOURNALS FREE ACCESS
    Measurements of vTrs and absorbed energy of 18%Cr steel and its welds by V-notch Carpy impact test were carried out in the temperature range from-80 to 140°C in order to clarify the effects of alloying elements on the toughness of the steel and welds. The specimens of welds were prepared from 3.2mm hot rolled andannealed plate by TIG (tongsten inert gas) meet run with I-grooved joint without filler. The toughness of the specimen was evaluated from the values obtained from the Charpy impact test.
    The main results obtained are as follows;
    1) The transition curves of the base metal and welds are remarkably shifted to lower temperatures with decreasing the contents of carbon and nitrogen and adding the proper amounts of titanium and manganese.
    2) The ductile-brittle transition temperatures lower to a large extent with adding the proper contents of titanium and also making the structure of steel become a single phase of ferrite.
    3) Manganese addition strengthens the weld metal by solution-hardening and simultaneously disperses the precipitation of flaky chromium carbides of M7C3 and M23C6, and consequently improves the toughness of the welds remarkably.
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