Director & Managing Executive Officer Yukinobu Kurashina

Ryohei Suzuki, Wei Lin and Masanori Ogata

Alumina-silica and spinel refractries were submitted to molten-steel dipping tests in order to develop anti-alumina-clogging refractries for the inside liner of a submerged entry nozzle that are characterized by the formation of liquid-bearing microstructure.

Alumina-silica refractories form a liquid-bearing reaction layer along the hot face via manganese invasion from the molten steel, but performance varies depending on the silica content of the refractory and manganese concentration of the molten steel.

Spinel refractories containing MgO, CaO and SiO2 as flux form a liquid-bearing texture by heating without reacting with the molten steel.

Alumina adhesion on the inner wall of submerged entry nozzles was reduced by applying the newly developed refractories.

Masakazu Iida and Kenji Suzuki

In order to describe the variations in the corrosion rate of the blast furnace main trough from the view point of furnace productivity, a mass transfer model was proposed.

In the model, the variations in productivity were taken into account as slag flow speed variations.

The calculated results were in good agreement with the observed data.

Thus, the accuracy of the alterations of trough repair schedule corresponding to the changes in the furnace production plan can be improved by utilizing the corrosion rate predicted by the model.

Makoto Nakamura, Wei Lin, Masanori Ogata and Masato Hashimoto

Ladle shrouds (LS) and SEN are mainly constructed of alumina-graphite (AG) materials, and recently carbon-free (CF) materials are utilized for the inside liner.

The CF inside liner has some superior characteristics for casting clean steels however one major challenge is thermal spalling due to high thermal expansion.

The CF liner acts as a heat insulator reducing thermal shock due to its low thermal conductivity.

Therefore when thermal expansion is reduced to a certain level, the CF liner is expected to improve thermal-spalling resistance of the LS and SEN.

Through an investigation on various materials, we have developed the CF materials with relatively low thermal expansion.

The effect of thermal expansion and conductivity on the thermal stress of the LS is evaluated by FEM.

Conventional CF materials cause large thermal stress compared to LSs without CF liners.

However, low thermal-expansion CF materials reduce thermal stress at the neck through a heat-insulation effect, reducing uneven temperature distribution.

Takuya Imaoka and Yukimasa Iwamoto

Durability of submerged entry nozzles (SEN) used in the continuous casting process of molten steel is generally limited by the corrosion of the ZrO2-C (ZG) materials used in the powder line.

The effects of mold powder compositions on the dissolution rates and destabilization phenomena of ZrO2 grains were investigated.

The addition of alkali metal oxides and alkaline-earth oxides to the base mold powder accelerated the dissolution rate of ZrO2 grains, but it did not affect the destabilization phenomenon.

Reduction of SiO2 and F suppressed the destabilization of ZrO2 grains, which reduced the corrosion rates observed in actual usage.

Yuki Niiya, Masatsugu Kitamura and Akihito Kajitani

Considering the adhesion behavior in tapholes of commercially operated blast furnaces, adhesive strength of taphole mixes involved a slag in bonding plane were evaluated.

As a result of the evaluation, it was suggested that pitch-added alumina rich taphole mixes are suitable from the view point of the adhesion behavior between the old body and new injected taphole mixes.

Atsushi Takata, Kenji Yamamoto, Tsunenobu Saeki and Mitsuhiro Kajimura

We have developed new sliding gate valve (SGV) mechanisms for Electric Arc Furnaces (EAF) tapping systems, to reduce slag contamination into the ladle during tapping.

New SGV mechanisms were used in a spout tapping EAF and a bottom tapping EAF, both of which are working well.

Shinobu Imai and Masamichi Takai

In electric arc furnaces(EAF) for steel making, the bottom purging tuyere that is used for gas agitation plays an important role in helping with the dissolution of scraps, homogenization of temperature, purification of molten steel and reduction in steel making hours.

This paper introduces a newly developed bottom purging tuyere with new gas supplying system, which achieved extended service life without changing the materials and the length of the tuyere.

Hiroaki Morii, Haruhiko Minami and Shinji Adachi

A new type of sliding gate plate called "ECO plate" has been developed.

The ECO plate can be reused several times by exchanging a small core plate installed at the bore area.

In the field trial, the performance of the ECO plate was the same as that of conventional plates even when reused twice.

ECO plates can contribute to the reduction of the customer's refractory cost and the amount of refractory waste.

Hiroyasu Niitsuma, Masanori Ogata, Ian Mclennan, Paul Cassar and Mark Camplin

At the No.2 and No.3 slab casters at Port Kembla Steel Works of BlueScope Steel in Australia, there was a strong drive to improve the steel flow pattern and anti-clogging countermeasures in order to improve the steel quality.

By the application of the Annular Step SEN with a carbon free liner combined with multi layer porous upper nozzle, alumina clogging incidence in the SEN was drastically decreased.

In order to achieve stable casting with less alumina clogging incidents, it is very important to have a synergy effect of appropriate Ar gas practice, configuration of the SEN and materials of the SEN.

Hisashi Tomiya, Tomoaki Takisawa and Tomoaki Takisawa

In the steel making processes, ladles are widely used as transporting containers and/or refining facilities of molten steel.

Recently, solutions for improving not only the durability but also the environmental issues are strongly demanded.

We have various kinds of high performance ladle bricks to satisfy these requirements.

Kiyoyuki KOMATSUBARA, Hisaharu SASAKI and Takaaki KOYAMA

We have developed new high-performance repair mixes for BOF hot repairs.

New carbon bonded gunning mixes adhere much better than ordinary gunning mixes even when sprayed onto brick surfaces hotter than 1300oC, which is the typical temperature of a BOF side wall shortly after slag discharging.

The curing times of the new hot casting mixes are much shorter than those of ordinary ones, which contributes shortening the repair time.

These new repair mixes, gunning and hot casting, are being used successfully in actual applications.

Tatsuya HIROTANI and Masakazu IIDA

Adhesion and penetration of coal tar are typical issues of precast blocks used for coke oven doors.

Glazing on the block surface is an established technology for preventing such adhesion and penetration.

We have developed glazed panel installed precast blocks by applying this glazing technology.

They are performing well in actual applications.

Atsushi Makiya, Yoshikazu Kida and Masahiro Yoshikawa

Our high-silica ceramics are fabricated by sintering high purity powder.

They exhibit excellent properties of not only chemical, thermal and fracture resistance, but also freedom of shape.

Currently, we have proposed application of the products to several markets.

Motomichi Suzuki, Kentaro Uemichi and Hidenao Suzuki

Isolite offers "ALF Series" as an original product to users handling molten aluminum.

Three types of ALF have been developed.

We summarize the general features and the quality differences among them here.