At Sumangala Steel, we are constantly striving to innovate and improve our steel-making and rolling process. Today, Sumangala Steel's modern hot charging continuous rolling mill employs high standards to roll its quality steel billets into superior TMT bars.
A strict adherence to the best practices and technologies of the industry ensures Sumangala TMT bars are second to none.
It is this experiential knowledge and our in-depth understanding of steel, and the steel-making process that makes us stand apart.
We have distilled the art of steel making into 7 key factors
that we hold sacrosanct and test
ourselves against constantly.
The science of steel making is all about maintaining a balance between the alloying elements of carbon, manganese, and silicon, while minimizing impurities such as sulphur and phosphorus.
Carbon: This is an essential alloy to increase the yield strength of steel, however too much carbon makes the steel brittle.
Manganese: It enhances hardenability and deoxidizes the liquid metal improving its mechanical properties. Manganese in the right proportion to sulphur reduces the brittleness of sulphur.
Silicon: It is a vital agent used to remove oxygen and gases in steel improving its soundness thereby ensuring the steel is free from defects, decays, or damages.
Sulphur and Phosphorus: Both these are malefic elements and its presence in steel causes serious defects. Sumangala through its raw material blending and control ensures that these elements are minimized to well below standards.
Sumangala believes that the secondary steel making organically augments TMT bars with elements like copper, chromium and nickel that are found in ferrous scrap which enhance the corrosion resistance and strength of the bars at no extra expense.
The Thermo Mechanical Treatment is a superior process that imparts the critical mechanical properties to a TMT bar. Once the bar is rolled to required size, speed and temperature, water of the right quantity, temperature and pressure is sprayed on the bar. A critical control of these variables and process is of utmost importance to produce high quality TMT bars.
Quenching: The rolled hot bar of the given size at the right speed and temperature enters the quenching box of the TMT system, where the right quantity of water at the right temperature and pressure is sprayed to quench the red-hot steel in cold water.
Self Tempering: On leaving the quenching box the outer shell is cool as compared to the still hot core; which continues to radiate heat. This heat migrates towards the surface self-tempering the outer layer into martensitic thereby giving the bar improved deformity.
Thereafter the bars are allowed to cool on the cooling bed naturally. The continued radiation and migration of the heat from the core to the surface turns the Austenitic core into a ferrite-pearlite structure thereby ensuring a rigid outer layer with a ductile soft core.
TMT is used to reinforce concrete as it can take higher loads, redistribute forces, and when stressed is resilient enough to elongate (stretch) and revert to its original shape without rupturing.
Yield Strength in a reinforcement bar is the maximum yield stress (weight) that a reinforcement steel bar can bear before permanently losing its shape.
Tensile Strength is the maximum stress (weight) that a reinforcement steel bar can bear before breaking.
Breaking Stress is the point at which the stress on the bar exceeds the tensile stress causing it to rupture.
The grade of the TMT bar only specifies the yield strength of the bar, i.e., if the grade of the bar is Fe500, then the bar should be able to bear a load equal to 500 N/mm² before losing its integrity. This is an important factor in the design of concrete in structures. The consistency of yield strength across the length of the bar is critical.
The use of the reinforcement bar in structures is not only about load bearing strength, it is also about the flexibility that steel imparts to concrete.
Our carefully calibrated Thermo-Mechanical-Treatment process gives our TMT bar high ductility. This allows it the ability to stretch and bend without rupturing under load. This superior ductility ensures safety of structure under extreme conditions.
Ductility is measured by percentage Elongation. The higher the percentage elongation of the TMT bar in relation to the grade, the better it is.
Steel bars have to be fabricated to be embedded in concrete as per design requirements to be used as reinforcement. Therefore, TMT bars have to be bendable, weldable and workable.
Chemistry: The chemistry of steel plays a vital role with carbon and carbon equivalence being important influencers. Sumangala Steel’s ability to maintain close tolerance at the lower end of the requirement, ensures superior workability. Minimizing the sulphur and phosphorus in the steel ensures that the steel when bent does not rupture or crack.
Thermo mechanical treatment: A strict adherence to the consistency and geometry of the martensitic layer ensures a close control of the yield strength across the TMT bar. This ensures the bar is not hard, brittle, or eccentric. This is what ensures that our bars are highly workable without any risks.
The ideal bond between steel and concrete should make the resultant structure is monolithic. Bond strength is the resistance to the separation of the mortar and concrete from the reinforcing steel. The stronger the bond, the better (safer and structurally sound) the building.
The bond between concrete and steel is enhanced by scientifically ribbing the bar along its longitudinal (length) and transverse (width) surface. The rib and lug geometry are critical for high bond strength of a TMT bar. A scientifically derived geometry, and not just patterns that make the bar look attractive, is of paramount importance to bond strength.
The design of RCC dictates the quantum of steel required to be embedded in concrete, assuming a nominal section weight to reinforce the structure. However, steel is used by length while the quantum of steel actually embedded in the concrete depends on its section weight.
Therefore, the section weight of a bar is of monumental importance. If the section weight is higher than nominal more steel than required is consumed unnecessarily. If the section weight is lower than the minimum, less steel than needed is embedded in the structure, compromising its integrity