Presently, the best TMT steel bars in India are made using LRF (Ladle Refining Furnace) Technology as per the standard IS: 1786. This standard lays down the appropriate chemical composition and associated physical properties required to make construction grade steel bars.
To produce the best quality TMT steel bars, it is vital that the proportion of Sulphur and Phosphorous is well-controlled and kept within limits. If they are present in higher proportions, then the chemicals can drastically reduce the ductility of steel and produce inclusions which can damage the steel’s quality resulting in TMT steel bars with disastrous imperfections’.
In present-day steel making, once the steel is made in the basic oxygen furnace, arc furnace or induction furnace, it gets transferred into the ladle for more refining, chemistry adjustment, inclusion, modifications, etc. All these treatments take place in the ladle. As a result of which additional heat is needed to execute these operations.
This is where under LRF technology the ladle gets a heat source. This source heats the liquid metal and compensates for thermal losses. The furnace in which the liquid steel quality is improved by refining and heating is called a Ladle Refining Furnace (LRF).
WHAT IS LRF TECHNOLOGY?
LRF (Ladle Refining Furnace) Technology is a state-of-the-art technology that produces construction grade steel with iron ore as the raw material.
HOW IT WORKS?
Under the LRF Technology, the Ladle Refining Furnace helps improve the quality of liquid steel by raising the temperature. This helps in producing a more refined grade of steel.
What happens is during the steel production process, once the steel is made from iron in the basic oxygen furnace/arc furnace or induction furnace; it gets transferred into the ladle for further refining, chemistry adjustment, inclusion, and modifications. Then subsequently the ladle increases the temperature of the heat source and later adjusts the chemical composition of molten raw metal. This will elevate the heat of the liquid metal while at the same time compensating thermal losses. Later, it will refine the steel.
WHY IT’S HAILED AS A LANDMARK TECHNOLOGY?
Sulphur (S) and Phosphorous (P) are two critical elements in steel. With LRF technology, the steel bars are refined in terms of S & P in the induction route. It also helps float inclusions in steel and eliminate dissolved gases, eventually resulting in better quality TMT steel bars and steel.
LRF Technology has been hailed as a revolutionary technology because it
- Refines and purifies the steel by floating inclusions in steel and eliminating dissolved gases.
- Obtains the specified chemistry by adding ferro-alloys.
Then the refined steel is sent to the caster where it is casted into billets of required sizes in closed environment. This will facilitate further control of any remnant gases and other inclusions, eventually resulting in higher quality of TMT steel bars.
These high quality TMT steel bars are used in huge infrastructure projects that demand heavy load-bearing capacity, like bridges, dams, skyscrapers, ports, airports, malls, canals, tunnels, industrial structures, flyovers, etc. They are also ideal for use in high seismic zones or areas that are vulnerable to the fury of natural calamities posing a risk to people’s lives and properties.
BENEFITS OF LRF TECHNOLOGY
LRF technology involves
- Desulphurization of steel;
- Removal of oxide inclusions;
- Homogenization of the temperature and composition of molten steel by gentle stirring;
- Degassing of steel through inert gas purging. This helps achieve low gas content (hydrogen, nitrogen, and oxygen);
- Saving on ferro alloys consumption through better recovery and maintenance of composition in narrow range;
- Improvement in grain refinement in the microstructure;
- Enhancement of productivity. This ensures emptying of melting furnace earlier at low temperature; &
- Acting as a buffer by holding molten steel for sequencing on the CCM.
As a result of the above process, the steel bars gets esulphurized and dephosperized; is made cleaner after being rid of oxide inclusions; & degassed resulting in low gas. The whole technology process is efficient culminating in superior quality steel bars. Presently, it is hailed as the most effective and efficient technology for producing high-quality ‘D’ grade TMT steel bars as per the IS: 1786 norms.
Without this technology, steel making furnaces will need to provide higher tap temperatures that result from heat losses during refining with conventional ladles.