Throughout history, the development of refractory materials and related technologies has largely progressed alongside or followed steel technology, primarily due to their application in steelmaking. Even within the half-century following World War II, the main trends in refractory materials, as discussed in previous chapters, have indeed encompassed a wide variety of aspects, directly related to the expansion and qualitative advancement of refractory technology itself.
Here, we select five items from these trends, the contents of which are as follows:
(1) Increased furnace life and reduced raw material energy consumption;
(2) Increased use of carbonaceous refractory materials;
(3) Shift towards higher-grade raw materials;
(4) Progress in mechanized and non-monomeric construction;
(5) Advances in furnace structure design, especially cooling technology.
Furthermore, there has been a significant trend in the development of refractory material manufacturing technology and corresponding countermeasures to environmental issues, which cannot be ignored and must be taken seriously.
In summary, significant progress has been made in the application technology and properties of refractory materials for steelmaking over the past half-century, resulting in substantial improvements in their effectiveness. This can be seen from the average consumption of refractory materials shown below:
In 1960, the price of steel was 77.0 kg per ton.
In 1990, the price of steel was 11.5 kg per ton.
So, what are the underlying reasons for these developments?
In terms of the magnitude of the impact, changes in steel manufacturing processes can be considered to play a significant role. Like all other materials, refractory materials have also experienced leaps in manufacturing and application technologies due to changes and innovations in the market (applications). In particular, the increasing size and pressure of blast furnaces, the shift from open-hearth furnaces to converters, the transition from ingot casting to continuous casting, and the emergence of secondary refining—these successive new processes, comparable to the 19th-century Industrial Revolution, have had a profound impact on refractory materials.
Among refractory materials where the quality of raw materials directly impacts product quality, advancements in raw material quality have a significant influence. The emergence of large-scale raw material manufacturing processes, along with changes in social and economic conditions, have also had a certain impact. In particular, the increasing demand for mechanization in furnace lining and repair work is the primary reason for the rising usage of monolithic refractories. The increased importance of monolithic refractories has spurred technological advancements and is related to heightened environmental concerns, leading to new countermeasures in the use of coal tar and chromium oxide-based refractories.
Technological advancements and technology transfer from adjacent fields such as non-ferrous metals and glass, as well as related fields such as planned equipment and powder technology, have also played a crucial role. Especially after 1960, changes in the composition of refractory materials technology increased the importance of communication with other fields. Taking temperature as an example, even from a general perspective, historical practical effects show that steel refractory materials face more technical obstacles compared to other fields due to the high temperatures involved in both manufacturing and use. Other fields with lower temperatures act as pioneers, leveraging developed technologies and making improvements. The technology transfer from the non-ferrous metals sector in continuous casting is a good example, linking the concept and technology of ceramic spraying on metals with the development of spray-plating repair technology.
Steel Ladle Refractory Materials: Overview and Their Importance in the Foundry Industry
Steel companies require high-quality refractory material solutions to achieve maximum production efficiency and minimum costs. The structure of ladle refractory materials is customized according to the operating conditions of each plant to optimize refractory material service life and output.
A complete solution for ladle safety and working liners: including the bottom, sidewalls, and slag discharge line.
Overview of Refractory Ladle Lining
The refractory lining of a steel ladle is crucial. It imparts high-temperature resistance and durability, enabling it to withstand extreme temperatures and extend its service life. However, with prolonged use, the lining can be damaged by high temperatures. After long-term continuous use, the ladle lining thins, at which point the outer surface of the ladle will feel noticeably hot. All of these factors can lead to increased ladle temperature and even pose a danger during operation.
Brickwork and monolithic safety lining
There are three most common designs for steel ladle safety lining bricks: an arch-wedge structure, providing one of the tightest safety linings; a book-brick structure, enhancing protection against steel penetration; and a semi-universal structure, which is easy and quick to install.
Monolithic safety linings can be installed using either cast-in-place or shotcrete methods. Cast-in-place methods create very dense and geometrically precise safety linings, but require specialized casting molds. Shotcrete is a moldless construction method, but its precision is not as high as cast-in-place. However, the final geometry can be improved by laying a half-inch-thick dry vibratory layer, which separates the shotcrete safety lining from the working lining.
Brickwork and monolithic working lining
One major advantage of brick lining is that the ladle can be quickly reused after relining because the refractory material requires very little time to dry.
Integral working liners require carefully designed molds and sufficient curing and drying time and facilities before the ladle can be put into use. A major advantage of integral working liners is that worn liners can be refurbished, thus reducing downtime.
Steel Ladle Refractory Lining: Key Advantages
- High-performance, high-volume steel ladles
- Reliability under extreme operating temperatures
- Improved resistance to thermal shock
- Resistance to slag corrosion
- Resistance to mechanical erosion
- Extended service life
- Reduced production costs
- Reduced conversion costs
A word of caution regarding the long-term use of a ladle
The ladle refractories that the iron and steel industry use must be maintained and well taken care of. They need minute inspection at regular intervals to make sure the lining is intact. In case the lining of the ladle is found eroded, then it needs to be relined without any delay so that it can function properly. In cases where timely maintenance activities are not performed, ladles can cause a sudden breakdown in the production process. Under these circumstances, an immediate replacement is the only way left to resume the work again.
A look at the bricks for the ladle
Fired Doloma Bricks: Usable in ladle slag lines, carbon-free bricks for production of ultra-low carbon-containing steels, minimal oxygen resupply to the steel, and excellent price-performance ratio.
Magnesia Carbon Bricks: Universal usability in all areas of the wear lining, carbores or resin bonded, highest refractoriness, unparalleled flexibility for different and even changing process conditions.
Fired Alumina Bricks: Ideal products for bath area, safety lining, and insulation of ladles, high thermal shock resistance, and low thermal conductivity, available in many different raw material combinations.
Fired Magnesia Bricks: Exceptional products restricted to special applications, products for safety linings, and special wear lining applications, available as pure burnt magnesia or combined with either chromium oxide or direct-bonded oxicrom.
Tempered Doloma Bricks: Usable in all areas of the wear lining, good coating behavior in silicon killed steel shops, carbores or resin bonded, and excellent price-performance ratio.
Alumina-Magnesia-Carbon Bricks: Optimal for impact area, usable for bath area especially in alumina killed steel shops, and highest erosion resistance.
Ladle circulation cycle
Ladle circulation cycle is the time that a ladle takes to complete one circulation cycle. This cycle is considered to be very important for better functions of the steel melting shop. Generally, it takes various hours from one steel taping to the next steel tapping in a ladle. The time it takes determines how many ladles are required to keep things in motion. Some of the major steps involved in the ladle circulation cycle include the following:
Inspection and maintenance of STL
STL is what holds liquid steel at extreme temperatures. The range includes 1600 degrees C to 1650 degrees C. The high temperatures and a large number of other processes that need to be carried out in the STL can cause significant wear in the lining. Therefore, proper inspection and maintenance are required to keep it always in good shape.
Ladle preheating
After the inspection and maintenance, STL needs to be preheated to bring the ladle inside temperature as per the requirement. In case the ladle inside temperature is already at the suitable level, then the preheating step can be avoided.
Liquid steel tapping
The molten material (steel) needs to be tapped into the STL from the principal steelmaking process. When it is tapped, an utmost precaution is required to make sure the ample freeboard is available in STL to process further refining.
Ladle transportation
The transportation of STL with liquid steel is made generally through a transfer car to the secondary refining processes. In this important step, waiting of the ladle is avoidable for excellent control of temperature loss.
