The HYQST technology ensures a uniform quality across the bar. The proof is a perfect ring that can be seen across any cross-section of the bar.
JSW NEOSTEEL is manufactured at JSW Steel – Vijaynagar Works and JSW Steel – Dolvi works. It is manufactured using virgin iron ore. JSW NEOSTEEL is toughened high strength HYQST (High Yield Quenched and Self Tempered) TMT Bar conforming to IS 1786:2008,. TMT are hot-rolled from steel billets are subjected to the thermo-mechanical treatment. The HYQST technology ensures a uniform quality across the bar. The proof is a perfect ring that can be seen across any cross-section of the bar.
Stages of TMT manufacturing
1Conversion of iron ore to molten iron
ASourcing and processing of Raw Material
The raw material viz. iron ore, coal/coke and the fluxes (limestone and dolomite) are sourced from their respective locations and are stacked, reclaimed and blended in the required proportion.
BBeneficiation, Agglomeration and conversion of coke to coal
The iron ore is beneficiated to increase the iron content in it. Then, the iron ore fines are agglomerated into pellets and sinter to enhance productivity. The coal is converted to coke for later use.
CIron making
Coke, ore and sinter are fed, or ‘charged’, into the top of the blast furnace, together with limestone. A hot air blast is injected through nozzles in the base of the furnace. This causes reduction of iron ore and the iron in the ore and sinter is melted out to form a pool of molten metal in the bottom, or hearth, of the furnace. The limestone combines with impurities and molten rock from the iron ore and sinter, forming a liquid ‘slag' which, being lighter than the metal, floats on top of it.
2Conversion of molten iron to steel and continuous casting
APre treatment and primary steelmaking
The molten iron is subjected to pre treatment and is converted to steel in a convertor or a Basic oxygen Furnace. Oxygen is blown into the BOF which contains the molten iron from the blast furnace. This oxygen combines with carbon in the iron and carbon is eliminated in the form of carbon di oxide.
BSecondary Steelmaking
The steel is further subjected to Ladle heating for refining the chemistry of the steel. This is done in a Ladle Heating Furnace (LHF) and RH De-gasifier
CContinuous Casting
In the continuous casting process the molten metal is poured directly into a casting machine to produce billets, with a cross section 165mm2
3Hot rolling and thermo mechanical treatment
AQuenching
When a hot rolled bar leaves the final mill stand (including roughing mill, intermediate mill, finishing mill, etc.), it is instantaneously quenched 9 a type of heat treatment where the rebars are rapidly cooled to obtain certain material properties) using a special water spray system in the quenching box. This is done to harden the surface while the core still remains hot and soft.
BSelf-tempering
After leaving the quenching box, the core continues to supply heat to the surface since it is at a relatively higher temperature. This causes the tempering of the outer martensitic layer into a structure called Tempered Martensite. The core stays austenitic (a typical cubical crystalline structure) at this stage also.
CAtmospheric cooling
Post the self-tempering, the bars are subjected to atmospheric cooling (at room temperature) on special cooling beds where the austenitic core gets transformed into a ductile ferrite-pearlite structure. The final structure, thus is a perfect combination of a strong outer layer (tempered martensite) with a ductile core (ferrite).
Due to the partial quenching (heat treatment), the micro structure of the bar consists of Tempered Martensite in the periphery and Ferrite Pearlite in the centre The strength to the bar is by Tempered Martensite layer while the ductility to the bar is incorporated by the Ferrite- Pearlite layer.
The perfect balance of strength and ductility in JSW Neosteel TMT bars results in a highly safe design with minimum use of reinforcement and at the same time making the structure safe against the action of earthquakes.
Watch the entire manufacturing process