Trishul 500 TMT Process
The Thermo-Mechanical Treatment (TMT) process involves rapid quenching of hot bars at specific temperature with controlled pressure and travel ratio. The bars are then passed through water jacket after finishing stand as per the diameter of the bar which ranges from 8mm to 32mm. This process is controlled completely by a computerised software program, which maintains accuracy on final product, eliminating the possibility of human errors in order to obtain the required mechanical properties. Such case-hardened bars give high-yield and ultimate tensile strength. Due to the soft-core, they help in maintaining a higher elongation percentage, and exhibit a bend and re-bend property that plays a vital role in all normal and earthquake zones.
Raw Material Processing
Raw materials such as Sponge Iron/DRI, Billets and B-boms are chemically and physically graded. The chemical structure is thoroughly analysed using in-house Spectrometer and C & S apparatus. If the required specifications are not met, the raw materials undergo a process control procedure. If the raw materials meet the desired specifications, then they are safely stored in the Raw Material Yard.
Melting
The selected raw material sample is added to lab furnace for melting in a core-less induction furnace. The furnace is composed of a refractory container capable of holding the molten bath, which is surrounded by water-cooled helical coil connected to a source of alternating current. After melting, the furnace is tilted to remove the slag and other impurities that come to the surface of molten metal. To refine the molten metal, Micro-alloying elements are then added, and if necessary, de-surfacing and de-phosphorising are done to remove all gases present. Throughout the process, samples are constantly analysed to ensure accurate and desired chemical composition.
Purging Process
The molten metal tapped to the ladle undergoes a Gas Purging process to retain thermal homogeneity, and to remove excessive non-metallic inclusions.
Casting Process
After purging, the material is taken from ladle to a tundish and from the tundish to moulds in the continuous casting set-up. Liquid steel is poured into moulds to replenish the withdrawn steel at an equal rate, which depends on the cross-section, and the grade and quality of the steel being produced. Thereafter, the steel strand enters a Roller Containment Section and Secondary Chamber. The strand is sprayed with water or air mist for solidification and then cut to sizes.
Re-Heating Process
The solidified strand undergoes a re-heating process, where billets are re-heated up to the crystallization temperature. The fuel used for this process is Producer Gas, which is achieved by gasification of solid fuels like coal or biomass in the Gasifier. Re-heating using Producer Gas is very eco-friendly and ensures uniform temperature of billets. The billets are then pushed into re-heating in a temperature controlled furnace at 1150°C to 1180°C.
Rolling Process
Once the billets reach the desired rolling temperature, they are brought out from the furnace and made to pass through the Roughing Stand, where the process of gradual size reduction of billets begins. The size is further reduced in the Intermediate and Finishing Mills, till their desired size is obtained. Roller Bearings fitted on the Roll Neck prevent unnecessary deformation of the bar. The Lop Scanner in the flow of the bar helps tensionless rolling, ensuring perfect round shape of the bar. This process of gradually reducing the billet size is paramount to ensure finer grain structure.
Quenching Process
The solidified strand undergoes a re-heating process, where billets are re-heated to reach the crystallization temperature. The fuel used for this process is Producer Gas, which is achieved by gasification of solid fuels like coal or biomass in the Gasifier. Re-heating using Producer Gas is very eco-friendly and ensures uniform temperature of billets. The billets then are, pushed into re-heating furnace at temperatures controlled at 1150°C to 1180°C.
Rolling Process
Once the billets reach the desired rolling temperature, they are brought out from the furnace and made to first pass through the Roughing Stand, where the process of gradual size reduction of billets begins. The size is further reduced in the Intermediate and Finishing Mills, till their desired size is obtained. Roller Bearings fitted on the Roll Neck prevents unnecessary deformation of the bar. The Lop Scanner in the flow of the bar helps tensionless rolling, ensuring perfect round shape of the bar. This process of gradually reducing the billet size is paramount to ensure finer grain structure.
Quenching Process
At this stage, another round of testing is done, and if accepted, the bars are fed to a Quenching Box at a very high speed. Here, rapid and controlled water quenching is performed to drastically reduce the surface temperature from 950°C to 300°C.
Self-Tempering Process
During the quenching process, only the outer portion of the bar (case) gets quenched, while the inner part (core) remains hot. So it is passed on to the Cooling Bed, where the core that is still hot, transfers the heat to the case outside, thereby tempering it. Due to this self-tempering, the Martensitic case becomes Tempered Martensite, with more strength and corrosion resistance properties.
Cutting, Bending and Dispatching
Once the bars are cooled, they are straightened and cut into desired lengths by means of cold shear. They are again inspected for chemical and physical properties, and then stored in the Finished Goods Yard. Accordingly, on receiving customer orders, C & B Section cuts and shapes desired sizes bars, and after complete conformation to the customer requirements, they are dispatched to exact site schedules.