Present Status and Future Development of Alloy Design
Michio YAMAZAKI
pp. 17-23
Abstract
[in Japanese]
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ONLINE ISSN: | 1883-2954 |
PRINT ISSN: | 0021-1575 |
Publisher: | The Iron and Steel Institute of Japan |
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21 Nov. (Last 30 Days)
Michio YAMAZAKI
pp. 17-23
Abstract
[in Japanese]
Tsuguharu UEDA, Katsukiyo MARUKAWA, Shoji ANEZAKI
pp. 24-31
pp. 31-31
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Tetsu-to-Hagané Vol.47(1961), No.13
Tetsu-to-Hagané Vol.69(1983), No.3
Satomi YAMAMOTO, Kazumi HARASHIMA
pp. 32-41
Abstract
Change in chemical composition of slag during the refining of hot metal with Na2CO3 under the condition of top-oxygen blowing in the temperature range from 1 280 to 1 450°C was studied.
Violent decomposition of Na2CO3 in the presence of [C] was observed at the beginning of experiments. However, total amount of Na evaporated from slag during the experiment was not conspicuous. Rate of vaporization of Na was found to decrease with decreasing reaction temperature and with increasing contents of acidic compounds in the slag, such as SiO2 and P2O5.
Judging from material balance calculation for S, some part of charged S was considered to be transferred to waste gas. Chemical analysis of the dust and slag indicated that the preferential vaporization of S and Na from the slag occurred. Vaporization loss of P was not detected by chemical analysis of dust and slag. However, the study with thermal-balance showed that Na3PO4 reacted readily with graphite and converted to CO, P and Na above 1 000°C.
Aribumi NIIDA, Kazuo OKOHIRA, Arata TANAKA, Tsuyoshi KAI
pp. 42-50
Abstract
Experiments have been made to study the crystallization process of free lime and magnesia from the molten LD-converter slag saturated with magnesia.
Many types of free lime exist depending on the cooling conditions and the slag basicity. In rapidly cooled slags with a basicity higher than 4, two types of free lime exist, i.e. primary lime solid solution (Lpri) and lime solid solution (Lper) as residuum which results from a peritectoid reaction between Lpri and the liquid slag. On the other hand, in slowly cooled slag, three types of free lime exist.
1) CaO rich phase (Lwus) which contains a lot of minute precipitates of white spots of wustite.
2) Lime (LC3S) as a mixture of 2CaO·SiO2 and lime solid solution which are formed by the decomposition of 3CaO·SiO2.
3) Lime (Lres) which exists in the form of a string along boundaries of 2CaO·Fe2O3 crystals.
Free magnesia forms a solid solution with FeO or/and MnO in slag and changes into magnesio wustite (MW).
The mechanism of the formation of such various phases is discussed.
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ISIJ International Vol.57(2017), No.2
Sumio KOBAYASHI, Akio HATONO, Ken KATOGI, Akira KURIYAMA, Kiyoshi ICHIHARA
pp. 51-59
Abstract
A microwave method to measure directly the level and the reflectivity of the slag in a BOF has been developed, and successfully tested in a 150 ton BOF process. The measurement system is based on the FM radar technique. The results show that this method can be applied to predict slopping, and estimate the slag formation. Most of sloppings are observed when the slag level exceeds a certain critical limit and the reflectivity decreases under a certain level. Slopping predection criteria have been established after a series of measurements. Using the criteria, the slopping is predicted with a reliability of over 80% within 30 s before the event. The slopping control scheme using the microwave method has been established and the frequency of the slopping has been decreased to 1/5 of the uncontrolled heat. The microwave system is now in on-line operation at Wakayama Works of Sumitomo Metal Industries.
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Toshikazu SAKURAYA, Kazumi MORI
pp. 60-66
Abstract
Studies have been made on the rates of dissolution of stationary of rotated cylindrical iron specimens containing various amounts of oxygen into molten carbon-saturated iron alloys. The explored temperature range was from 1 200 to 1 450°C. The highest oxygen concentration of the specimen was 1.14%. The dissolution rate was determined from the rate of decrease in diameter of the cylinder.
In the case of stationary dissolution, oxygen in the iron specimen, that is, the evolution of CO was found to have a marked effect on the dissolution rate. This phenomenon is shown to be analogous to the mass transfer at a gas evolving electrode. At high oxygen contents of the specimen, a phenomenon analogous to nucleate-film boiling of liquid over a hot solid surface was observed. The highest dissolution rate which was observed at 1 400°C for iron containing 0.96% oxygen was 590 times as large as the lowest rate observed at 1 200°C for aluminum-killed iron.
In the case of rotational dissolution of oxygen containing iron specimens, at lower rpm the rate was controlled mainly by the extent of CO evolution. At higher rpm, the effect of rotation became predominant.
Yoshio UKYO, Kazuhiro S. GOTO
pp. 67-72
Abstract
Thermoelectric powers of zirconia base solid electrolytes and liquid PbO-SiO2 system have been measured in air in the temperature range from 700° to 1 600°C. Electrode at higher temperature side was the negative pole for zirconia electrolytes (oxygen anion conductor), whereas electrode at lower temperature side was the positive pole for molten PbO-SiO2 system (lead cation conductor).
The absolute thermoelectric powers of the oxide systems have been calculated by substracting the EMF of the virtual cell reaction and thermoelectric power of platinum electrode from the measured total electromotive forces.
Those are in range of -0.37 to -0.51 mV/K for the solid Electrolytes and of 0.06 to 0.013 mV/K for the liquid silicate. Physical meanings of these values arn dicussed.
Hidemaro TAKEUCHI, Shogo MATSUMURA, Yasunobu IKEHARA, Tadaaki KOMANO, Takashi YANAI
pp. 73-79
Abstract
Effects of electromagnetic stirring on cast structure of continuously cast austenitic stainless steel slabs were investigated to improve the macropattern of plates by grain refinement of cast structure. The following results were obtained: (1) It was shown that cast structure of austenitic stainless steel slabs can be refined by electromagnetic stirring at high casting temperature. The proper conditions for obtaining a high ratio of equiaxed crystals were ascertained. (2) The qualities of austenitic stainless steel plates manufactured by continuous casting with electromagnetic stirring were improved and homogeneous macro structure of plates were obtained at low reduction.
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Yoshinori WAKAMATSU, Masami ONISHI
pp. 80-86
Abstract
In hot dip galvanizing reaction, as previously reported, iron-zinc intermediate phase layers are formed successively in the order of the ζ, palisade δ1, Γ, Γ1 and compact δ1 phases, and their growth does not follow the parabolic law. In order to speculate rate controlling process in the galvanizing reaction, in this paper, growth curves of the intermediate phase layers formed by galvanizing reaction at 460°C are calculated numerically using Wagner's diffusion equation on the moving velocity of phase boundary.
The results obtained are as follows:
(1) The calculated growth curves fit well with those obtained experimentally in a previous study.
(2) The characteristic growth kinetics of palisade δ1 layer, decrease in growth rate accompanied by formation of compact δ1 layer and twice rapid growth after appearances of Γ phase layer and of compact δ1 layer, could be explained by use of Wagner's equation.
(3) The growth rate of the intermediate phase layers in galvanizing reaction seems to be controlled by diffusion process.
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Tetsu-to-Hagané Vol.89(2003), No.1
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MATERIALS TRANSACTIONS Vol.44(2003), No.5
Jiro JIZAIMARU, Hidenori SHIRASAWA
pp. 87-96
Abstract
Effects of controlled rolling conditions on strength and toughness of Mn-Mo-Nb steels were compared between their structure of ferrite · pearlite and of bainite. The change in strength and toughness with the rolling conditions between slab reheating and finish rolling was nearly the same with each other. The bainite steel showed superior strength and toughness to the ferrite · pearlite steel. Toughness of the bainite steel decreased with increase in bainite area fraction resulted from the variation of controlled rolling conditions.
The investigation was also extended to the effects of cooling rate and coiling temperature, as cooling parameters after controlled rolling, on strength and toughness of Mn-Mo-Nb bainite steels different in carbon and molybdenum contents. Both strength and toughness of these steels were improved by increasing cooling rate and lowering coiling temperature, although these conditions resulted in the increase in bainite area fraction. These mutually contradictory effects of bainite area fraction on toughnss of bainite steel were attributed to the difference in appearance of bainite and size of the coexisting polygonal ferrite.
The remarkable increase in toughness caused by the accelerated cooling rate after finish rolling corresponded well to the increase in area fraction of the extra fine (1-2μ) polygonal ferrite which nucleated on the deformation band of unrecrystallized austenite and remained small during cooling.
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Tetsu-to-Hagané Vol.70(1984), No.5
Masaru YAMAMOTO, Yasushi HORIUCHI, Ohmi MIYAGAWA, Dai FUJISHIRO
pp. 97-106
Abstract
Effects of morphology of grain boundary carbides and grain boundary configuration on low-cycle fatigue properties were investigated at 700°C with various strain wave-forms, using an austenitic heat resisting steel SUH 38 (JIS) precipitation-hardened by M23C6 carbides. In ordinary straight grain boudaries, fatigue life decreased remarkably with decreasing strain rate in triangular or sawtooth strain wave-forms and increasing hold time in trapezoidal one, due to intergranular cracking induced by creep deformation during strain cycling. In particular, the notable decrease in fatigue life due to creep damage occurred in unsymmetrical strain wave-forms where the creep deformation accumulated only during tensile straining. The zigzag grain boundaries with coarse carbides could prevent an intergranular cracking by virtue of the retardation of grain boundary sliding and the good coherency between coarse grain boundary carbides and matrix. Consequently, grain boundary strengthening by zigzag boundaries could improve remarkably the fatigue life even in unsymmetrical strain wave-forms where the ordinary straight boundaries caused a drastic creep damage.
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Tetsu-to-Hagané Vol.69(1983), No.14
Tetsu-to-Hagané Vol.69(1983), No.12
Masaru YAMAMOTO, Yuhji OOTSUKA, Ohmi MIYAGAWA, Dai FUJISHIRO
pp. 107-116
Abstract
Effects of grain size, γ' particle size and grain boundary configuration on high-cycle fatigue properties of a Ni-base superalloy Inconel 751 were studied over a wide range of temperature up to 900°C.
Below 750°C, fatigue life increased as grain size decreased because of the slower propagation rate of fatigue cracks which generated along coarse slip bands. When the temperature raised up to 900°C, the intergranular cracking became predominant with decreasing grain size since dislocations could be readily released from pile-ups by recovery and intergranular oxidation might be accelerated, while transgranular cracking still remained in coarse grained specimens. The propagation rate of intergranular cracks was so much higher as compared with the transgranular ones that the maximum fatigue life at 900°C was attained at the specimen of medium grain size in which the mixed trans- and inter-granular cracking occurred. Zigzag grain boundaries with coarse carbides had not a beneficial effect on the fatigue strength and fracture mode at 900°C even when the intergranular cracking took place. It was also found that effects of γ' particle size and temperature on fatigue strength were related not only to changes in dislocation-particle interaction with particle size, but also to temperature dependence of γ' strength of particle itself.
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Tetsu-to-Hagané Vol.67(1981), No.1
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Tetsu-to-Hagané Vol.70(1984), No.5
Kiichi NARITA, Kotaro YAMAMOTO, Kazuyo KANAMONO, Chikako HAYASHI
pp. 117-125
Abstract
A study has been made on the behavior of precipitates in niobium or titanium and niobium-containing centrifugal cast heat-resisting steels (HK40, HP and IN519) during creep rupture test at 1 050°C.
(1) In the as-cast condition, iron chromium carbide of M7C3 type precipitates, except for steel IN519 (0.33%C-24%Cr-24%Ni) where M23C6 type precipitates. Titanium niobium carbonitride (MX) precipitates in the steel containing titanium and niobium, and niobium carbonitride (NbX) precipitates in the steel containing only niobium. Chromium nitride (Cr2N) precipitates except in the steel containing only niobium.
(2) During creep rupture test, M7C3 in the as-cast steel changes to (Cr0.85Fe0.15)23C6. As the results of nitriding by air, Cr2N increases and complex nitride, (Cr, Fe)NbN of tetragonal lattice, precipitates in the niobium-containing steel. Moreover, substitution reaction proceeds between carbon and nitrogen or between titanium and niobium with change of lattice parameter.
(3) M23C6, Cr2N and A1N are completely decomposed by hydrochloric acid (1+1) at 90°C. By the same acid M7C3, MX and NbX are decomposed gradually but (Cr, Fe) NbN is hardly decomposed.Based upon the differences in chemical stability of precipitates, the chemical composition and amount of each kind of precipitates can be successfully determined.
Taketomo YAMAZAKI, Takashi ZAIZEN, Shozaburo ASAMI, Tomohisa SOMURA
pp. 126-135
Abstract
The crystal structures of oxide films formed on the surface of 17% Cr-Fe alloys containing various amounts of Mn and Si, when treated in H2-H2O atmospheres with dew points of - 25° and - 36°C, were investigated. The influence of the oxide films with different crystal structures on the corrosion resistance of alloys to dilute sulphuric acid was also studied.
The results obtained are as follows:
The alloys form (Cr. Fe)2O3, MnCr2O4 and SiO2, depending on the content of Mn and Si, even when the oxygen potentials (dew points) of the atmospheres are those that would normally produce a Cr2O3 film on pure Cr-Fe alloys. These oxides show less resistance to corrosion than Cr2O3.
A pure 17% Cr-Fe alloy forms only Cr2O3 and exhibits especially excellent corrosion resistance. However, 17% Cr-Mn-Fe alloys with a small amount of Mn in the range of 0.08 to 0.25% appear to form spinel type (MnCr2O4 etc) oxides and have a different behavior in their resistance to corrosion. The minimal corrosion rate is attained at 0.08% Mn, beyond which the corrosion rate increases as the Mn content increases. On the contrary, the 17% Cr-Si-Fe alloy with a Si content of 0.10% forms (Cr. Fe)2O3 and SiO2. When the Si content is increased beyond 0.10%, (Cr. Fe)2O3 disappears and Cr2O3 forms, improving corrosion resistance.
The corrosion resistance behavior of the alloys mentioned above can be explained by the variation of the crystal structures and thickness of the oxide films formed under varying controlled atmospheres.
Shinsaku MATSUYAMA
pp. 136-144
Abstract
To make clear the major factor determining the critical strength for delayed fracture of high strength bolts exposed to moist atmosphere, the role of interdendritic microsegregation bands in hydrogen assisted delayed fracture of a quenched and tempered steel has been investigated.
In interdendritic segregation bands enriched in Mn which promotes the segregation of P at prior austenite grain bounderies, hydrogen makes it easy to produce intergranular cracking. From these observations, it may be concluded that delayed fracture of high strength bolts is controlled by intergranular cracking in a microsegregation band which exists in the triaxially stressed region.
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ISIJ International Vol.59(2019), No.1
Yoshikuni KAWABE, Seiichi MUNEKI, Junji TAKAHASHI
pp. 145-152
Abstract
The effect of prior austenite grain size on fracture toughness (KIC) in 2 750MPa grade 13Ni-15Co-10Mo maraging steel has been investigated. The prior austenite grain size was varied in the range of 760Oμ using both thermomechanical treatment and solution treatment.
KIC increased with increasing the grain size. For example, KIC increased from 2OMPa·m1/2 for 8μ to 30MPa·m1/2 for 500μ and varied linearly with the reciprocal square root of the grain size. The acoustic emission measurement during fracture toughness test and fracture surface observation at the tip of fatigue precrack revealed that subcritical crack growth of intergranular fracture mode occurred as the grain size increased and KIC was apparently increased due to the microbranching effect of the crack front. On the basis of the above observation, it was suggested that true grain size dependence of KIC in 13Ni-15Co-10Mo steel might be less than the experimentally obtained result.
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Takashi OHTSUBO, Akihiro MIYASAKA, Hiroshi YASUDA
pp. 153-162
Abstract
A new technical method has been developed on the analytical system which can provide us with the information about the phase of nonmetallic elements, such as carbon, sulfur and nitrogen, in steel.
When a finely-milled steel sample is isochronally heated in a hydrogen stream, nonmetallic elements react with hydrogen forming hydride-gases. The hydrides are at real-time analysed by a mass-spectrometer in relation to the heating temperature. From the temperature and the amount of gas detected, the phase of nonmetallic elements in steel is analysed.
Takashi OHTSUBO, Akihira MIYASAKA
pp. 163-168
Abstract
Nitrogen extraction curve obtained by the hydrogen hot extraction (HHE) technique was discussed from a view point of diffusion of nitrogen in steel.
By a numerical analysis, a theoretical temperature-extraction curve was obtained on the assumption that the rate-determining reaction was the diffusion of dissolved nitrogen in steel and by using the measured particle size of the test sample and the heating rate of the routine HHE analysis as a base of the calculation. And the time required for extraction of nitrogen at different temperature was calculated. The theoretical curve was very similar to the one obtained by the experiment.
It was proven that the particle size and the heating rate, which had been adopted for the routine HHE analysis, were satisfactory for the HHE differential determination between free nitrogen and precipitated nitrogen in steel.
Minao ITO, Shoki SATO, Masanao NARITA
pp. 169-176
Abstract
In Japanese Industrial Standards (JIS), the method of using iron base binary calibration curve is adopted for X-ray fluorescence analysis of steels, and is defined to be applicable to the analysis of nickel base alloys. In this report, some problems were studied for applying the JIS method to the analysis of practical nickel alloy samples. Also, the correction factors of interelement effects suitable for those practical samples were determined. Moreover, the method of using nickel base binary calibration curve was compared with that of using iron base binary calibration curve, the JIS method, for the analysis of nickel base alloys. As the result, the accuracy of both methods had no difference and it was comfirmed that the method of using iron base binary calibration curve was applicable to nickel base alloys, even if the content of iron was less than 10%.
戸澤 宏一, 糸山 誓司, 菅原 健, 青木 孝夫, 升田 博之
pp. 184-185,180
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