Advanced TMT Technology
SASM steel TMT bars are produced using the most advanced thermo mechanical treatment (TMT)available worldwide. The raw material is produced through an integrated steel-making process, using virgin iron ore treated in a gas-based sponge iron plant. It is further refined in an electric arc furnace using ladle furnace technology. This result in pure steel devoid of undesirable impurities like Sulphur & Phosphorus.
The integrated steel plant billet or slab is subsequently hot rolled through an automatic PLC controlled rolling mill into high strength SASM steel 500W TMT Bars having consistent mechanical properties and dimensional control. The hot rolled bars are treated with the on-line thermo mechanical treatment through the following process –
The bars leaving the final mill stand at about 900ºC and are passed through a specially designed quenching box. The red hot bars are then subjected to sudden and intense cooling with a specially designed water spray system. The cooling time and rate depend on the size of the bars, and are controlled by maintaining a desired temperature and flow rate in the cooling box. The surface gets quenched allowing the outer layer of the bar to a reduced temperature of 500ºC to 550ºC and forms a hard martensite structure, while the inner layer remains comparatively hot and austenitic in nature.
Once the bar leave the quenching box, the core remains hot as compared to the surface, allowing the heat to flow from the core to the outer surface causing tempering of the outer martensitic layer into a structure called ‘Tempered Martensite’. The core still remains austenitic at this stage.
The bars are finally placed on the cooling bed where the core is air-cooled into ductile-ferrite-pearlite structures. Thus the final structure of SASM steel 500W TMT bars consist of a combination of a strong outer layer with a ductile core giving them the optimum combination of high strength & ductility.