Tetsu-to-Hagane

Ironmaking

Regular Article

Development of an Evaluation Method of Pulverized Coal Combustion Utilizing Emission Intensity of Potassium Spectroscopic Analysis

Shinroku Matsuzaki, Masahiro Nagata, Kazuhiro Nishihara

2013 Volume 99 Issue 5 Pages 329-337
Published: 2013
Released on J-STAGE: April 30, 2013

DOIhttps://doi.org/10.2355/tetsutohagane.99.329

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We examined the use of spectroscopic analysis as a method of evaluation of the situation of the pulverized coal combustion. The results of the basic combustion flame test using a butane gas burner and the basic test apparatus, we found the possibility that the combustion process of the pulverized coal was able to be understood from the luminescence spectrum of potassium of ash in the pulverized coal.
The combustibility of various lances was evaluated with the basic test apparatus and a real blast furnace. As for oxy-coal lance and double lance, it has been understood that combustibility improves it under the low excess air ratio from the spectroscopic analysis. However, it is influenced from the injected gas volume about oxy-coal lance.
There is theoretically a possibility that the temperature can be presumed from the half-width of the luminescence spectrum. The correlation of the half-width and the temperature was able to be confirmed from the experimental data. However, it is necessary to develop the experiment technique to presume an actual temperature because resolution of spectroscope is low.

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Development of Two-Color Thermometer Using a Color CCD Camera and Measurement Technology of Tuyere and Raceway of Blast Furnace

Shinroku Matsuzaki, Masato Sugiura, Masahiro Itoh, Kazumoto Kakiuchi, ...

2013 Volume 99 Issue 5 Pages 338-345
Published: 2013
Released on J-STAGE: April 30, 2013

DOIhttps://doi.org/10.2355/tetsutohagane.99.338

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The temperature of the tuyere and the raceway shows the state of the combustion of the pulverized coal and the state of circling of the coke and the dropping state of the un-reduction ore. Thus, it is a key factor for the estimate of the state or stability of under cohesive zone and raceway structure.
Therefore, to measure the state of the temperature of the raceway quantitatively, two color thermometer using color CCD camera was developed. This thermometer can be measured a long term and continuously without being able to measure two dimensional and disturbing the measurement because it is noncontact. Moreover, the influences of optical attenuation such as dust and dirty window compared with the radiation thermometer are not received easily.
In addition, we found the possibility that a structural change in the raceway was able to be detected by making the temperature of a measurement point all images a histogram and evaluating the average, standard variation, skewness, and kurtosis.

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Surface Treatment and Corrosion

Regular Article

Electrodeposition Behavior of Zn-Co Alloy from Alkaline Zincate Solution Containing Triethanolamine

Hiroaki Nakano, Shitoku Shibata, Shingo Arakawa, Satoshi Oue, Shigeo K ...

2013 Volume 99 Issue 5 Pages 346-351
Published: 2013
Released on J-STAGE: April 30, 2013

DOIhttps://doi.org/10.2355/tetsutohagane.99.346

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Electrodeposition behavior of Zn-Co alloys was investigated at current densities of 2–500 A∙m⁻² and a charge of 5 × 10⁴ C∙m⁻² in an unagitated zincate solution containing triethanolamine, which forms a stable complex with Co²⁺ ions at 308 K. At low current densities below 5 A∙m^–2, the Zn-Co alloy exhibited normal codeposition, wherein electrochemically more noble Co deposited preferentially, while at high current densities above 6 A∙m^–2, it exhibited anomalous codeposition, wherein less noble Zn deposited preferentially. The current efficiency for Zn-Co alloy deposition was low to be about 20% in the region of nomal codeposition at low current densities, while it was 95% in the region of anomalous codeposition at high current densities. In the region of anomalous codeposition at high current densities, the partial polarization curves for Co deposition and H₂ evolution were significantly shifted to less noble direction by coexisting of Zn²⁺ ions, showing the formation of an inhibitor for deposition, which results from Zn²⁺ ions in the cathode layer. In contrast, in the region of normal codeposition at low current densities below 5 A∙m^–2, the underpotential deposition of Zn apparently occurred with Co. Because Zn-Co alloys are composed of the stable intermetallic compounds of CoZn₁₃ and Co₅Zn₂₁, the activity coefficient of Zn in the deposit appears to decrease remarkably.

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Transformations and Microstructures

Regular Article

Tensile Behavior of Ti,Mo-Added Low Carbon Steels with Interphase Boundary Precipitated Structures

Naoya Kamikawa, Yoshihisa Abe, Goro Miyamoto, Yoshimasa Funakawa, Tada ...

2013 Volume 99 Issue 5 Pages 352-361
Published: 2013
Released on J-STAGE: April 30, 2013

DOIhttps://doi.org/10.2355/tetsutohagane.99.352

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Tensile behavior and structure-property relationship of ferritic steels with nano-sized carbide dispersion were invesigated using Ti-added steel and Ti,Mo-added low carbon steels. By austenitizing followed by isothermal heat treatment at 700°C, polygonal ferrites containing very fine carbides of TiC and (Ti,Mo) C were obtained in the Ti-added and the Ti,Mo-added steels, respectively. The size of such carbides was finer in the Ti,Mo-added steel than in the Ti-added steel at the same holding period of isothermal heat treatment. The results of tensile tests for these samples showed that the strength is higher as the diameter of the carbides is smaller. The structure-based strength calculation led to a good agreement with the experiments, when it was assumed that the Ashby-Orowan mechanism is dominant for precipitation strengthening of nano-sized alloy carbides. It was also suggested that a relatively large tensile ductility is related to enhanced recovery during the tensile deformation, accompanied with promotion of secondary slips or cross slips in a finer scale due to the nano-sized particles.

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Quantitative Analysis for Solid Solution Content of the Microalloy Elements in Steel

Satoshi Kinoshiro, Tomoharu Ishida, Masao Inose, Kyoko Fujimoto

2013 Volume 99 Issue 5 Pages 362-365
Published: 2013
Released on J-STAGE: April 30, 2013

DOIhttps://doi.org/10.2355/tetsutohagane.99.362

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For the steel making control with the microalloy elements, it is essential to accurately analyze the solid solution content or precipitation content of the microalloy element in steel. The electrolytic extraction - filtration method has been used to determine all precipitations in steel, and the content of solid solution is obtained by the subtraction of the precipitation content from total content. But it has become inadequate to analyze the fine precipitates because some of the fine precipitates are unavoidably uncollected. Hence, we have developed a quantitative analysis for solute elements in steel by using of analyzing a portion of the electrolytic solution. By electrolysis, solute elements are dissolved into the electrolyte, and the precipitates remains on the surface of the sample. So, the analysis of the electrolytic solution during or after electrolysis enables the determination of solid solution content directly. For certified reference materials, the sum of the total content of solid solution determined by this method and the precipitates determined by the conventional method substantially agrees with certified value. However, for the samples that contain fine precipitates, they are not in agreement with the total content obtained by the spark-OES. It is estimated that the precipitates not collected by filtration in the conventional method cause the disagreement. It shows the proposed method, which analyzes solute solution directly, is useful.

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Mechanical Properties

Regular Article

Evaluation of Microstructures and Mechanical Properties of Steel with Tensile Loading Process Using X-Ray Line Profile Analysis

Masayoshi Kumagai, Takuya Kikuchi, Muneyuki Imafuku, Shin-Ichi Ohya

2013 Volume 99 Issue 5 Pages 366-372
Published: 2013
Released on J-STAGE: April 30, 2013

DOIhttps://doi.org/10.2355/tetsutohagane.99.366

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X-ray line profile analysis, modified Williamson-Hall method/modified Warren-Averbach method, was carried out to measure microscopic parameters such as dislocation density and crystallite size of S45C steel with tensile loading after released. As the result, X-ray line profiles were broadened after yield process due to convolution of increase of dislocation density and refinement of crystallite size. Correlations between microscopic parameters and macroscopic parameters such as flow stress, plastic strain, and Vickers hardness were also discussed. Then followings were clarified, relationship between flow stress and dislocation density that measured by X-ray diffraction agrees with conventional relationship,τ = τ₀ + κμbρ^1/2, which had been obtained by TEM observation and etch-pit technique; plastic strain after plateau region has relationship to dislocation density, ρ = ρ₀ + Dε_p^m, which means it is able to measure plastic strain by X-ray diffraction; Vickers hardness relates to square root of dislocation density as linear function.

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Gigacycle Fatigue Properties of Double-Melted SCM440 Steel and Size Effects

Yoshiyuki Furuya

2013 Volume 99 Issue 5 Pages 373-379
Published: 2013
Released on J-STAGE: April 30, 2013

DOIhttps://doi.org/10.2355/tetsutohagane.99.373

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Ultrasonic fatigue tests up to gigacycle regimes were conducted for double-melted SCM440 low-alloy steel using enlarged and conventional specimens, comparing the results with those of single-melted steel. Although both types of specimens of the double-melted steel showed internal fracture, the difference between the enlarged and conventional specimens was very small in spite of large difference in case of the single-melted steel. The inclusion sizes of an internal fracture origin also showed negligible difference between the two types of the specimens. Namely, size effects were small in case of the double-melted steel, unlike the case of the single-melted steel. These results meant that the double-melted steel showed superior gigacycle fatigue properties to the single-melted steel when the enlarged specimens were used in the fatigue tests, while the superiority was invisible when conventional specimens were used. Moreover, when the inclusion sizes were evaluated by the enlarged specimens, the double-melted steel showed much smaller inclusion sizes than the single-melted. Hence, using the enlarged specimens was highly advisable in evaluating the gigacycle fatigue properties and the inclusion size, particularly in case of high-cleanliness steels.

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Physical Properties

Regular Article

Lattice Defects of Cold-drawn and Aged Fe-36wt%Ni Alloys and Effects of Additions of C and V on Hardness and Thermal Expansion

Kazuo Nakama, Shinichi Furuya, Kazuki Sugita, Koji Inoue, Yasuharu Shi ...

2013 Volume 99 Issue 5 Pages 380-389
Published: 2013
Released on J-STAGE: April 30, 2013

DOIhttps://doi.org/10.2355/tetsutohagane.99.380

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Fe-36wt%Ni invar alloy has been widely used for precision parts where dimensional changes with temperature are unfavorable. In the viewpoint of industrial application, high-strength with low-thermal-expansion alloys are in increased demand for structural members such as power cables and electronic devices. Additions of alloying elements to and cold working on Fe-Ni alloys are effective methods that enable the alloys to strengthen, although these modifications also influence the magnitude of thermal expansion. In this study, effects of additions of 0.2wt%C and/or 0.8wt%V on hardness and thermal expansion of cold-drawn and aged Fe-36wt%Ni invar alloys are reported. Hardness in solution-treated and as-drawn conditions increased with addition of C, and, when both C and V were added, hardness of the alloy reached its maximum after aged at 650°C. Besides an increase in hardness with addition of any of C and V, thermal expansion below Tc became smaller in as-drawn condition than in solution-treated condition. Measurements of positron lifetimes revealed that vacancies introduced by cold-drawing were annealed out through aging up to 300°C and dislocation motion was activated at 500°C. Both vacancies and dislocations, especially C-dislocation complexes, seemingly influence the decrease in thermal expansion. While graphite precipitation in the C-added invar alloy showed no hardening, addition of C and V to invar alloy resulted in secondary hardening by vanadium carbide precipitation when aged over 500°C, which realized high-hardness and low-thermal-expansion.

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