Tundish Heating
Continuous casting is now the predominant technology for steel production. To meet both the quality and productivity needs of the steel producer, tundish plasma heating is fast becoming an integral part of the casting process.
Tetronics has been at the forefront of high temperature plasma technology for over 40 years – successfully generating commercial turnkey solutions for the steel industry and others. With over 25 systems now installed worldwide, Tetronics is the clear market leader, its plasma heating systems representing the state-of-the-art of this high temperature technology. Tetronics offers total engineering solutions that include concept, design, installation, commissioning and maintenance. Tetronics’ tundish plasma heating systems can be retrofitted to existing steel casting plants as well as incorporated into new installations. We have supplied innovative plasma tundish heaters to companies around the world including:
- CORUS, UK
- CARPENTER, Sweden
- KAWASAKI, Japan
- NIPPON STEEL CORPORATION, Japan
- SUMITOMO, Japan
- NKK, Japan
- POSCO, South Korea
- SOLLAC, France
Our tundish plasma heating systems have demonstrated improvements in cast quality and productivity, which in turn have generated significant increases in annual revenue for steelmakers.
The Facts
Since 1987 Tetronics has been providing world-class tundish plasma arc heating technology to assist steelmakers in their drive for higher quality and productivity through improved temperature control.
It is well documented that inadequate control of casting temperature can lead to problems of segregation, internal and surface defects, undesirable micro-structures, reduced casting rates, increased rejection rates and, in extreme cases, breakouts. As a consequence, steelmakers have invested large sums of money in technology to control and monitor steel temperature through the steelmaking process.
Increasing numbers of steelmakers are turning to Tetronics plasma arc heating technology for improved temperature control in the tundish. Over 25 tundish heaters have been supplied by Tetronics to many of the world’s leading steel companies. Grades of steel cast with plasma include low, medium and high carbon steels, low and high alloy steels and stainless steels. Tetronics tundish heaters have been fitted to a variety of caster types including slab, billet, bloom and horizontal casters. The highly strategic position of the tundish as the point to perform final adjustments to steel temperature, combined with equipment that is reliable, versatile and cost competitive make Tetronics tundish plasma heating a compelling technology for all steel plants.
Technology
The plasma heating system transfers heat to the molten steel by direct arc heating. Early systems used a single cathodic plasma torch with a return electrode installed in the lining of the tundish.
In 1995 Tetronics developed and successfully introduced an improved system. The TwinTorch™ system consists of two plasma torches of opposing polarity, resulting in higher maximum powers and reduced modification to existing equipment. The TwinTorch system delivers excellent performance and reliability, and is the system of choice in modern continuous casting.
Ongoing product improvement of the technology since 1995 has delivered even greater levels of equipment reliability, reduced installation costs and longer torch life.
The full span of casting rates commonly employed in continuous casting can be satisfied as follows:
- Up to 5.0 tonnes per minute: one TwinTorch™ system
- Greater than 5.0 tonnes per minute: multiples of TwinTorch™ systems.
The TwinTorch system uses two plasma torches of opposing polarity. The current path is completed between the two transferred arcs by conduction through the steel. Innovative torch design ensures that both torches have the following characteristics:
- Use of argon as the plasma gas, to avoid contamination of the steel by nitrogen
- High efficiency and low gas use, for low operating costs
- Fine power adjustment and high turn down ratio, for accurate temperature control
- Simple construction, for rapid maintenance on the casting floor
- Small size and weight, for ease of handling and reduced water cooling losses.
The tundish roof and the tundish dam/weirs are modified to create a self-contained ‘heating chamber’, where a controlled atmosphere of argon is maintained to prevent oxidation of the steel or nitrogen pickup by excluding the ingress of air.
These dams and weirs are also used to direct the flow of the steel under the plasma arcs for maximum heat transfer efficiency and, together with the modifications to the tundish roof, are the only modifications required to the tundish and tundish car.
Tetronics provide all essential supporting services, including control and monitoring of plasma gas and torch cooling water, supply and monitoring of plasma power, torch manipulation, data acquisition and control systems to the customers’ requirements.
