Director, Managing Executive Officer Yuji YOSHIMURA

Masanori OGATA

This paper presents the change in development trends of refractories in Japan in the past half century. The development trend is roughly divided into three period. The 1st period was “quality improvement”, while the 2nd period was characterized by “change in quality” to cope with the change in the steelmaking process. In the 3rd stage, some new characteristics were added to products in order to differentiate them from imported refractories. And, the keyword for refractory development has shifted from “unit consumption” to “environment”. Currently, labor productivity, raw material risks, and production energy for raw materials are pointed out as challenges faced by the Japanese refractory industry.

Naohide HAMAMOTO, Takayuki MATSUNAGA and Masakazu IIDA

Slide valve (SV) plates are important refractories used to control the molten steel flow discharged from the ladle and tundish. SV plates are required to have high quality in order to control the flow rate accurately. In this article, we report on various SV plate materials, which were developed in accordance with demands of adaptability to various steel grades and longer life. By combining the structural evolution such as the SV plate shape with these new materials, it is possible to improve casting stability as well as SV plate durability.

Masayoshi KAKIHARA, Ryoma FUJIYOSHI, Atsuhisa IIDA and Hiroki YOSHIOKA

Development of the multi-hole plug (MHP) type bottom blowing tuyere for the converter is described in this paper. According to the microstructural studies on used tuyere, thermal spalling, which is caused by large thermal gradient near the hot face was determined to be the critical factor of MHP wear. Assuming that improvement of fracture toughness is essential to reducing wear, we developed high fracture toughness tuyere brick by applying matrix reinforcement (MTR) technology that optimizes size, shape and configuration of grain. In addition, Pitch impregnation of the burnt body (PIB) technology allowed carbon bond strengthening. Tuyere bricks to which both MTR and PIB technologies are applied (MTR-PIB brick) possess high fracture energy compared with ordinary material. Thus, spalling was prevented and the wear rate in actual service was significantly reduced with the MTR-PIB MHP tuyere brick.

Daisuke TANAKA, Tatsuya KAGEYAMA, Akihito KAJITANI and Yuga YAMAMOTO

We investigated the influence of Al2O3 fine powder addition on taphole mix properties after longtime heating. As a result of tests, it was confirmed that there was a small change of property and chemical composition after long-time heating in the SiC type samples not containing Fe-Si3N4. The molten iron corrosion resistance and slag also changed depending on the Al2O3 fine powder content in the matrix. It was also confirmed, on the other hand, that the apparent porosity increased, strength decreased and β-SiC and Si2N2O were markedly generated along with the decomposition reaction of Si3N4 after long-time heating in the Si3N4 type samples including Fe-Si3N4. The corrosion test indicated that Si2N2O generated from Si3N4 improved the molten iron corrosion resistance and Al dissolution in Si2N2O caused by Al2O3 fine powder addition contributed to both the molten iron corrosion resistance and to the inhibition of the slag penetration of the matrix. It is presumed that the addition of Al2O3 fine powder to taphole mix is effective for improving the corrosion resistance and the durability of the sedimentary deposit under the condition of prolonged high temperature exposure in the furnace.

Kosuke OTA, Kazuya NAKABO and Shigefumi NISHIDA

Alumina-spinel castable is known to have excellent volume stability. However, the marked expansion phenomenon was observed according to the kind of the dispersant added. The expansion of alumina spinel castable has been considered to be due to an increase in the amount of CaO･6Al2O3 produced. Contrary to this, it was revealed that Ca3(PO4)2 is generated by the addition of sodium polyphosphate and this caused castable expansion.

Yusuke OSHITA, Takayuki MATSUNAGA and Koji MORIWAKI

The slide valve (SV) plates for the continuous casting of molten steel are generically made of burned Al2O3-C materials. In specific, the corrosion resistance is very important when SV plates are used under arduous conditions such as special steel grade casting and so on. While adding Al to SV plate improves corrosion resistance, it deteriorates hydration resistance due to Al4C3 and AlN formed during burning. Therefore, high Al content Al2O3-C SV plate is generally unburned. But, oxidation of unburned SV plate at low temperatures frequently occurs. In this study, the effect of low temperature burning on each characteristic of high Al content Al2O3-C SV plate was investigated experimentally. The new material developed on the basis of the experimental results showed high durability compared with the unburned material.

Hisashi TOMIYA, Koichi IGABO and Kentaro HIRAYAMA

Basic refractories such as MgO-C and magnesia-chrome are widely used in secondary refining facilities with a vacuum function such as RH and VOD. However, use of MgO-C results in MgO-C reaction under reduced pressure and high temperature in the lower vessel of RH degasser. Damage of MgO-C seems to be increased by the structural embrittlement associated with the MgO-C reaction. As a result of various investigations, it was indicated that Spinel-C, which provides superior resistance to MgO-C reaction, may have excellent durability for the lower vessel sidewall of RH degasser.

Shoji TAKAHASHI and Junya ITO

Generally, mold powder for the continuous casting of steel contains fluorine in order to control the slag viscosity and the crystallization temperature. However, from environmental angles, etc., fluorine free mold powder has been required. Fluorine free conversion is possible for slab casting (low carbon, ultra-low carbon, and high carbon grades), bloom casting, billet casting, and beam blank casting, and fluorine free powders are currently being used in these cases. In this paper, the roles and impacts of fluorine in the mold powder and the method of fluorine free conversion are described.

Yuto SUZUKI and Kiyoyuki KOMATSUBARA

We developed coating material SCOAT-M-56 for the tundish, which can be used not only as a trowel coating material but also as a gunning material. This material has the improved characteristics of workability, drying property and dismantlability compared to conventional materials.

Kazunobu OGATA and Takahiro KAGO

We developed porous brick HSP209 with improved corrosion resistance by pore size refinement. According to the laboratory evaluation, HSP209 showed corrosion resistance approximately 30 % higher than a conventional product. As a result, the wear rate was reduced approximately 30 % in actual use, and durability improvement was confirmed.

Tsuyoshi SUWA and Tamiatsu KOYAKE

The penetration and structural deterioration resistance of chrome-free brick ELK-12XL-1 for the burning zone of the cement rotary kiln was improved by using magnesia grains with better sinterability. In the burning zone, the penetration depth of foreign components is deeper. Deep peeling with large thickness due to coating desorption and structural deterioration due to temperature change accompanies coating desorption. It is expected that application of ELK-12XL-1 will make it possible to operate the cement rotary kiln more stably.

Kazuki IGAMI, Atsuji KOBIKI and Kenji IKEDA

Recently, we are facing remarkable progresses of manufacturing technology and changes of raw materials. Along with these trends, the requirements for the performances of inorganic paints and adhesives have become diverse and sophisticated. In this paper, we introduced some examples of the application of our products. We would like to keep striving not only to improve our current products but also to develop new applications and products. We would be more than happy if you are of interested in our products and give us inquiries or requests.

Takeshi MIYAKE and Atsushi SUEYOSHI

Microporous insulation materials with heat resistance to 1400 ℃, low thermal conductivity, excellent processability and water resistance was developed. Fine pores give the conventional microporous insulation materials low thermal conductivity and excellent heat insulation. However, the use of the microporous insulation materials was limited due to the crystallization of silica, which lead to the disappearance of the micro pores at about 1100 ℃. Because of recent development, microporous insulation materials with high thermal performance can now be used at high temperature places.

Nobuhiro OTSUKA and Atsushi MAKIYA

Shinagawa Fine Ceramics Co., Ltd (SIFCE) have been recommending SNB, which is a composite ceramic material consisting of silicon nitride (Si3N4) and boron nitride (h-BN), as a material for metal atomizing spray nozzles. SNB has excellent thermal shock resistance depending on the property of h-BN, and it is possible to control the characteristics by changing the amount of h-BN. By adding zirconia (ZrO2) to SNB, corrosion resistance against molten metal is improved, and it is possible to reduce the corrosion damage during use as an atomizing nozzle. In the case of using nitride X instead of zirconia, the corrosion resistance is equivalent. Also, it is expected that the occurrence of “icicle” where the metal adheres to the lower end position (outlet position of molten metal) of the nozzle during atomization is reduced.