B. Rao

Improving Roof Life of Open Hearth Furnaces by Regular Cleaning

Roof Cleaning is one of the means adopted by different steel plants throughout the world for increasing the roof life of open hearth furnaces. With the adoption of basic roof in TISCO, it was observed that the roof was getting over-heated and the tabs holding the bricks were getting cut. This resulted in premature failure of roof requiring frequent hot repairs. It was presumed that the dust accumulation in the roof was acting as insulation altering the thermal gradient and enhancing the liquid migration deeper in the brick. Laboratory investigation confirmed this assumption. In TISCO, roof cleaning has been undertaken regularly to overcome this problem which has resulted in improving the roof life considerably. The practice has been extended to the silica roof also with considerable success.

Repair and Maintenance Practices of Blast Furnaces and Hot Blast Stoves

In the past, there were a few major refractory failures in blast furnaces of TISCO, viz. hearth break-outs, damage to the throat lining, etc. These furnaces were repaired and put back to operation. Premature failures also were experienced in the hot blast stoves, particularly in the checkers. In this communication, a few such occurrences and the details of repair work done, have been discussed.

Development of Siliceous Slinging Material for Ladle Lining

In recent years, sand slinging process is being used for lining ladles in steel plants. The slung mixes are made from naturally occurring sands or mixture of synthetic grains with suitable binders.In our country, ladle bricks constitute a major tonnage of fireclay bricks in the steel plants. An attempt was made to use sand as lining material in steel ladles to reduce the consumption of refractories and also to save time in relining.Work was undertaken to develop sand slinging mixes of proper composition utilizing indigenous sand. The mixes were tried in steel ladles, used for transferring blown metal from bessemer shop and hot metal from mixer to open hearth furnaces.

Evaluation of Checker Bricks for Blast Furnace Stoves

Currently, the stoves of blast furnaces are operated at a higher temperature for increasing productivity. Consequently, the demand on the quality of checker bricks has increased. In TISCO, the blast furnaces are operated at a hot blast temperature of 900°C. An attempt has been made to evaluate the refractories available from indigenous sources. Various physical and chemical properties of the bricks have been analysed along with their mineralogical constituents. Compressive creep characteristics have also been evaluated.

Effect of Different Additives on Soluble Silicate Bond

Soluble silicate (sodium silicate) has been used as bond in ceramic and refractories industry for a long time. The versatile nature of this material resulting from alkali silica reaction offered several advantages in many fields of refractory application. Additional advantages with respect to strength and rapid setting can be obtained by incorporating foreign ions, which reacted with colloidal micelles of silica in solution. Studies were undertaken with different additives for finding out the effect on strength and setting characteristics with aluminous and siliceous base materials. The mixtures were fired at various temperatures and their properties were evaluated.

Development of Chemically Bonded Silica Bricks from Silica Waste

During the dismantling of coke ovens, large quantity of silica waste was recovered and an investigation was undertaken to find out suitable means to utilize these materials. The use of silica grog for making brick was restricted due to its high grain porosity and inversion of cristobalite at lower temperature which seriously affects the bond strength.Work was undertaken to develop proper composition with suitable binders for making bricks utilizing the silica waste. The bricks were made and tried in the ladles used for transferring blown metal from Bessemer Shop to Open Hearth furnace. Encouraging results were obtained in the initial trials.

Refractories for Iron & Steel Industry in India—The Future Trend

The process technology of iron and steel making is undergoing rapid changes throughout the world. Larger capacity blast furnaces and taller coke ovens are the order of the day. Basic oxygen steelmaking processes are replacing the conventional method of steel making in open hearth furnace. Vacuum degassing, continuous casting, slide gate valves etc are also gaining popularity.The service conditions required to be met by refractories in the modern iron and steel making units are very much severe demanding improved quality of materials.In India, some of the existing steel plants are on the threshold of expansion and a few mini steel plants are also being put up. All these units are expected to adopt some of the latest techniques in iron and steel making requiring improved quality of refractories which are not available in our country at present. The quality of refractories that would be required in future are reviewed in this paper with a view to focusing on the possibilities of manufacturing them indigenously.

Development of Carbonaceous Lining Material from Blast Furnace Trough and Runner

Smooth operation of blast furnace largely depends on a good cast house practice, i.e. on the maintenance of trough and runner. In Tisco, clay bonded ramming material was used for trough and sand was used for lining the runner. Both these materials required constant attention and involved heavy maintenance job. Carbonaceous lining material has been developed to overcome these difficulties and successfully used in the Plant. Details of the laboratory work on various compositions and their service performance have been discussed.

Development of Coating Material for Stopper Rod Sleeves

In Tisco, the stopper rod sleeves used are of moderate heat duty quality. During the teeming of low carbon highly oxidised steels, severe erosion of sleeves, resulting in stopper rod failures, posed a problem. A coating material was developed and tried on the sleeves which gave encouraging results. Coating of sleeves has been adopted as a regular shop practice.

Development of Phosphate Bonded High Alumina Monolithics

High alumina monolithic with phosphoric acid as a binder are being used extensively in metallurgical furnaces. Development work was undertaken in the range of 60 to 90% aluminous material with indigenous raw material, e.g. bauxite, kyanite and diaspore. Phosphate bond was developed with certain additives without being detrimental to the physical properties.