Director, Managing Executive Officer　　Toshihiko KANESHIGE

Masakazu IIDA

In Japan, coke producing technology has been developed in order to manufacture coke that satisfies the requirement of blast furnace operation since the majority of coke is consumed for the iron making blast furnace. In this article, the coke properties, of which blast furnace requires, and development of coke manufacturing process is reviewed followed by the brief description about coke oven refractories wear and the technology dealing with environmental issues.

Yuta HINO

The fatigue failure behavior of silica brick refractory materials was investigated at room temperature and high temperature. It was found that the fatigue failure life of the silica bricks increased significantly at temperatures over 1473K compared with that in the fatigue failure test at room temperature. The reason for this improved fatigue fracture life at high temperatures was examined in detail. It was deduced that longer fatigue fracture life of silica bricks at high temperatures is related to the generation of a slight amount of liquid phase. The length of the fatigue fracture life of the bricks was estimated to depend on the wettability between the solid phase and liquid phase, with poor wettability resulting in extended fatigue fracture life.

Seiji HOSOHARA

While the service life of coke oven was expected to be 25 to 30 years in 1960s to 1970s when coke ovens were actively constructed in Japan, many coke ovens over 40 years old are still under operation according to the development of diagnosis and repair technology. In this article, studies about coke oven refractories damage mechanisms, the observation techniques of the in-chamber status and repair technologies in Japan are reviewed.

Masakazu IIDA, Koichiro MORI and Shigeo TANIGUCHI

Silica bricks, C.SC, C.SCD and C.SCDD for coke oven construction or renovation and HRS and C.FS-98 for exchange repair are introduced. C.SC, C.SCD and C.SCDD correspond to the grades normalized in German standard (DIN) as KN, KD and KS, respectively. They have been widely applied to new coke oven constructions. HRS, with excellent thermal spalling resistance for hot exchange repair, has many successful results. The effectiveness of the extremely small thermal expansion from room temperature to high temperature of C.FS-98 will be validated in various commercial applications in the future. In this paper, characteristics of these silica bricks are described.

Shigeki UCHIDA and Katsushige IKEGAMI

The dense silica bricks －SCD brand produced by Shinagawa Refractories Co., Ltd.－ which had been used in Japan were analyzed. The bricks used for 24 years still had the original cristobalite coarse grains in the coke chamber side of the bricks. However, the coarse grains completely disappeared from the entire bricks in the bricks used for 44 years and seemed to change to fine grains bound with each other. The entire body of the used bricks was converted to tridymite phase. The tridymite crystals had grown with secular changes. However, there was a variety of differences in crystal size among three parts, that is, the coke chamber side, the center part and the flue chamber side of the used brick. In addition, features of the used bricks were investigated from the chemical composition, the apparent porosity, compressive strength and so on.

Shigeki UCHIDA and Katsushige IKEGAMI

Hot repairing silica bricks －HRS brand produced by Shinagawa Refractories Co., Ltd.－ which were used for 8 years in Japan were analyzed. In the coke chamber side of the used HRS bricks, they showed a decrease in non-crystalline silica and an increase in cristobalite, although the texture resembled that of unused HRS bricks. In the flue chamber side of the used HRS bricks, the amount of non-crystalline silica was reduced further than that in the coke chamber side and the amount of tridymite increased more than that in the coke chamber side, although the amount of cristobalite was almost the same as that in the coke chamber side. Further, the texture was in a state where coarse grains were micronized and changed to the binding of fine grains. Little occurrence of surface damage on the coke chamber side, the little penetration of external chemical compositions into the bricks, increase in strength and a tendency for the thermal expansion ratio to increase were shown in the present studies. Even then, the 8 years used bricks were supposed to be successively enabled.

Natsumi HIGASHIKAWA, Shigefumi NISHIDA and Masakazu IIDA

Dearing with current demands for coke oven as extending service life, increase in productivity, reduction of internal gas emission, and so on, applications of monolithic refractories and precast block have been suited. In this article, our monolithic refractories and pre-casted blocks for coke oven are introduced in association with current coke oven operation status in Japan.

Masakazu IIDA, Hidekuni NISHIGUCHI, Koichiro MORI and Yoichi NASU

In this report, the effectiveness of the suppression of coal tar pitch adhesion and long term stability of glaze coated burned block for the coke oven door is demonstrated according to laboratory evaluation as well as investigation results after 12 years commercial application. The desirable properties of this block are attributed to excellent material design of CST-A53, optimum glaze composition, and a carefully controlled manufacturing process. Application of this product reduces the door maintenance work load of adhered coal tar pitch removal, resulting in high coke oven productivity with limited numbers of maintenance operators.

Koichiro MORI and Hirohumi MASU

Approximately 40 years have passed since the CDQ system began to operate in Japan. The CDQ system has many advantages such as exhaust heat recovery, environmental improvement and coke quality improvement, hence its construction is expected to be increased in many countries. Since 1976, we have supplied bricks to 24 CDQs at 7 works for 3 companies. Our bricks have good bricklaying characteristics, contribute to stable operation and extend service life through material design, precise quality control during production and investigation of damage situations.

Atsuhisa IIDA, Masayoshi KAKIHARA, Minoru SUTO and Hidenori TADA

The recent development of our MgO-C brick technology which focuses on controlling the microstructure allows a wide extension of the variations in our product line up. It enables detailed optimization of brick arrangement corresponding to individually varied requirements. In this article, newly developed microstructure controlling technologies adopted for novel MgO-C bricks are introduced followed by a description of recommendable BOF brick applications taking operational condition into account.

Naoko DOI, Atsuhisa IIDA and Hisashi TOMIYA

The corrosion resistance of unburned Al2O3-MgO bricks was improved by focusing on the in-situ microstructure evolution associated with the spinel forming reaction. A suitable microstructure evolution was achieved by densification of a green body consisting of raw materials with an appropriate grain size distribution. The effectiveness of the improved materials was validated by a laboratory corrosion test as well as commercial application to a steel ladle metal line.

Jose C. D. PONTES Jr., Douglas F. GALESI, Leonardo F. M. SOUZA, Carlos F. LEÃO, Hiroaki MORII,
Kenji YAMAMOTO, Atsushi TAKATA and Toshio HORIUCHI

We have developed a new generation ladle slide-gate system called SST for molten steel flowrate control at steelmaking plants. SST has many advantages such as reduction of refractory consumption, reduction of component parts, shortening of exchange time and simplified refractory exchange work. Plate bricks for the SST are shaped to an optimum compact size based on thermal stress analysis and fixed by a unique fixation method. Those plate bricks provide higher performance due to the elimination of the stress concentration in the working region thereby avoiding crack formation in this critical region. In addition, the SST uses actuator power not only for moving the lower plate but also for loading and releasing the surface pressure, so that plate exchange work is much easier than that of a conventional gate system. SST has been used at ArcelorMittal Tubarão since May 2012 with plate brick consumption being decreased drastically. This paper describes the development and the trial results of SST at ArcelorMittal Tubarão in terms of refractory service life and various great benefits to steel ladle operation.

Altemar D. D. NASCIMENTO, Jose C. D. PONTES Jr., Gabriel M. PIGATTI,
Douglas F. GALESI, Leonardo F. M. D. SOUZA, Carlos F. LEÃO,
Makoto NAKAMURA, Yukio OKAWA, Toshio HORIUCHI and Tomoaki WAKAE

Preventing the alumina adhesion of submerged entry nozzle (SEN) is greatly important not only for prolonging its service life but also improving steel quality. Carbon-free liner (material) contributes to prevent alumina adhesion. The wear resistance of carbon-free liner is the key retaining its efficacy. We have studied the influence of trace carbon component in carbon-free material. We conclude that even small amount of carbon in carbon-free material gives negative effect on preventing alumina clogging. On the basis of this knowledge, we tested new carbon-free liner and it performed very well at an actual caster. 

Yoshikazu HANAFUSA, Hisashi TOMIYA and Koichiro MORI

Bottom electrode refractories are one of the essential products for ABB-type direct current electrical furnace. In this report, we would like to introduce our products and our customer's actual operational results.