Senior Managing Director Y. SHIMIZU

Kobe Steel, Ltd. T. UEYAMA and H. OKADA
Shinko Wire Co., Ltd. S. MAEDA
Shinagawa Refractories Co., Ltd. S. UCHIDA, T. KOYAKE and J. SAGAWA

In order to satisfy higher quality steel requirements, No.3RH degasser was installed in Kakogawa works in November 2004.
After the start of No.3RH operation, heats per day of existing No.1RH have been decreased and the ratio of high-quality steel, which requires long treatment time, has increased.
With such a considerable change in service conditions, the campaign life of No.1RH lower vessel has sharply decreased to a low level due to heavy wear of the bottom bricks and unusual wear of the throat bricks which results in the sudden shut down of the vessel.
In order to reduce the wear rate of the bottom bricks, repairing procedures and bottom brick material have been improved.
In addition, to preventing unusual wear of the throat brick, expansion allowance of the bottom bricks has been improved by using refractory cushion board while carefully managing bottom shell deformation.
With these improvements, wear rate of the lower vessel has markedly decreased and sudden shut downs caused by refractory troubles have also been reduced.
This paper describes these No.1RH refractory improvements and gives a structural analysis of the vessel lining which is ongoing.

ArcelorMittal P. COLLUCCI, M. HALLOUCHERIE and F. LECLERCQ
Sidermin SA D. VERRELLE and C. SCHILTZ
Shinagawa Refractories Co., Ltd E. IIDA and M. NAKAMURA

We studied some different softening point pitches as binders for Carbon bonded gunning materials and additive amount of another molar weight phenolic resin.
As a result we found a good composition which gives high adhesion strength, high adhesion rate and hardening time.
Based on the result. We used the developed item in a BOF and confirmed high adhesion ability and good durability.

K. KOMATSUBARA, H. SASAKI and T. KOYAMA

We studied some different softening point pitches as binders for Carbon bonded gunning materials and additive amount of another molar weight phenolic resin.
As a result we found a good composition which gives high adhesion strength, high adhesion rate and hardening time.
Based on the result.
We used the developed item in a BOF and confirmed high adhesion ability and good durability.

T. IIDA, K. ENOKI, M. KITAMURA and T.KAGEYAMA

Reduction of time and labor for trough repair has been one of the most important customer demand problems.
In this study we developed new self-hardening mixerless materials which can shorten installation time by almost 1/3 that of conventional castable installation due to no-mixing process and shortened hardening time.

M. KITAMURA, K. ENOKI, H. MORIYASU and Y. NASU

Recently, customers demand large sized refractories for blast furnace relining in order to shorten the repair work period and increase equipment utilization, however, manufacturing larger sized refractories with the ordinary manufacturing method of bricks has become more and more difficult because of manufacturing equipments restrictions.
In order to highly satisfy their demands, we developed large sized blast furnace tuyere blocks.
They have same or higher quality than ordinary bricks and are about six times as heavy as our ordinary maximum sized tuyere bricks.
It is possible to make single-piece tuyere refractories with no divisions with this new block.
We believe this new product can provide many advantages including shortening the repair work period and improvement of durability through good structural stability and high quality.

M. KAKIHARA, H. TADA and E. IIDA

MgO-C bricks have been used for BOF, RH and electric arc furnaces.
In some applications, the decrease in carbon content is required to solve durability and environmental problems.
However, the decrease in carbon content induces reduced spalling resisatnce.
In this study, a new pitch powder was examined in order to solve this problem.
The effect of this pitch addition and improvement of spalling resistance were investigated.
And low carbon MgO-C bricks with this new pitch were developed for the RH degasser vessel.
This report describes the fundamental characteristics of the new pitch powder, and improvement of spalling resistance by using this new pitch in low carbon MgO-C bricks.

H. SASAKI, K. KOMATSUBARA and M. NAMBA

Hot BOF taphole sleeve repair is usually performed with phosphate bond gunning mix added excess water.
But phosphate bond gunning mix has a short service life, and requires gunning work in front of the hot furnace.
On other the hand, pitch bond hot casting repair mix has good service life, and requires only throwing the mix into a furnace.
But it has the drawback of long hardening time.
The hardening time of the newly developed rapid hardening pitch bond hot casting repair mix was shorten by 40% compared to the conventional mix.
So it hardens in 30 minutes.
If 30 minutes hardening time can be realized and the developed rapid hardening hot casting repair mix can be used for and shorten sleeve exchange, it is possible to improve service life, constriction workload, working efficiency, and shorten sleeve demolition working hours.

M. NAMBA, H. SASAKI and K. KOMATSUBARA

The gunning is the most popular hot repair method for the RH degasser snorkel.
But, the gunned body easily peels off because of steam when dryness is slow during gunning.
If the curing time after gunning is short, a gunned body with insufficient dryness is used, durability becomes poor because of explosions.
In this report, quick drying hot gunning repair mix is introduced.
An actual furnace test has already been started, and quick dryness and good durability of the new gunning mix has been confirmed.

H. TOMIYA, H. TADA and E. IIDA

High Al2O3 bricks and carbon containing bricks have been widely used for steel ladle lining.
But they have some drawbacks such as poor corrosion resistance, heat loss, and so on.
Al2O3-MgO castable lining shows a good performance, but requires a big initial investment in mixers and installation equipment and a strict drying and preheating procedure to avoid steam spalling.
In order to solve the fore mentioned problems of conventional materials, "ALTIMA" unburned Al2O3-MgO bricks for steel ladles have been investigated and developed.
In this paper the features and characteristics of ALTIMA and its trial result at BlueScope Steel will be reported.

B. HE, J. GILMORE, T. SUZUKI, J. ITOH, Y. IWAMOTO and T. OMOTO

The technologies of near net shape caster are progressing, and many medium slab caster (100-150mm thick) is been operated in North America, Europe and China.
However, there are many problems on the steel quality, the operation and the mold powder such as cracks, sintering, sticker BO and incorrect of BO detector system by the characteristic of casting conditions.
We developed new mold powder for medium thick slab casters with high viscosity and good melting property to solve these problems.

T. MIYAWAKI, H. SASAKI and Y. TAKAKURA

We report on a new type of repair material for trowelling and gunning.
Patching can be performed by trowl in the case of a small area, or by gunning in the case of a large area.
This two way repair material is appreciated for it's endurance and good installation qualities by many customers.
In the case of LF ladle repairs, the repair material remained after 30heats.
So, the ladle life can be extended and refractory cost per charge can be reduced.

K. YAMAMOTO and M. OSADA

We secured good seal characteristics and improved our easy, simple submerged entry nozzle quick change system for continuous casting.

M. YOSHIKAWA, T. ICHIMORI and A. MAKIYA

Recently, instead of conventional metallic material parts, ceramic materials have become to be used to prevent dust generation in clean room in the electronic industrial field.
Ourα-sialon ceramics are original ceramics which have complex microstructures consisting of α type and β type silicon nitride crystals.
These ceramics can be used for ceramic rollers because they are excellent in abrasion resistance and the rolling fatigue properties.

S. TANIGAWA and H. SUMIMURA

The installation time was able to be shortened to 2/3 of the conventional by applying a continuous mixer to the installation of castables for the main trough in hot conditions.
Durability was almost equal to the past.

K. NAKASHIMA and K. HAYASHI

A unique lightweight castable consisting of ceramic fiber and refractory powder has been developed and commercialized by Isolite.
The following is a brief description of its properties and typical applications.