“What are the best quality TMT bars” is the most common question possibly asked by anyone who is about to purchase the rebars. And when it comes to the question of quality, from plant to dispatch, it all begins with better quality control in manufacturing.
In the blog, we will today shed light in detail on the nitty-gritty of TMT bar manufacturing and how the manufacturing process influences the overall quality of the TMT bars.
What Are The Major Components Of TMT Bars?
The Thermo Mechanically Treated bars are high-strength reinforcement bars with a strong outer core and a soft inner core. They are manufactured under a process mostly known as Thermo Mechanical Treatment.
Steel is an alloy of iron, carbon, and other major elements that are extremely important for building ships, automobiles, tools, machines, etc. Because of its high tensile strength along with protection from corrosion, fire, and other environmental and accidental factors, the TMT bars ensure structural integrity, safety, and longevity.
The manufacturing process gives birth to different grades of TMT bars like – Fe-415, Fe-500, Fe-550, and Fe-600. The numbers signify the level of stress that can deform it and higher grades mean strength and superiority of the bars.
TMT Bar Manufacturing Process
Steel undergoes various processes that increase its mechanical properties like hardness, ductility, and yield strength. Thermo Mechanical Treatment (TMT) include mechanical or plastic deformation processes such as forging, rolling, etc with thermal processes like heat treatment, water quenching, and so on.
The production of best quality TMT bars typically relies on three major factors:
Quality of raw materials.
A well-designed automated rolling mill stand.
Applying modern quenching and tempering technology.
1. Transforming iron ore to billet
While the raw materials are still in their liquid form, it is placed in the furnace and treated with hot gas so that the molten state of iron is converted into steel. The liquid form of steel is then transferred into a casting machine to get the billets.
2. Changing of billets into steel
When the billets have attained the desired rolling temperature, they are passed through 1 stand, i.e. Roughing stand, with the help of a rolling conveyor. This process gradually reduces the size of the billets, which continues until the required size is achieved. This process ensures the finer grain structure of the bar and prevents any unnecessary deformation.
3. Thermo Mechanical Treatment
This is the last step in the manufacturing process of the TMT. However, it involves three major sub-steps.
Quenching
Self Tempering
Atmospheric cooling
Quenching
Quenching is responsible for offering hardness and ductility to the steel bars. The hot rolled steel bars are fed into the "Thermex System," a water spray system, as soon as they leave the mill. During this process, the inner core of the steel bars stays hot and pliable while the outside layer rapidly cools and becomes harder. The TMT bars are "quenched" during the entire operation.
Self-tempering
Following the bar's quenching process, the material cools, and the temperature inside the bar rises similarly to the outside. The outer structure gets tempered because of the heat being transported from the core to the exterior. This results in a temperature transfer from the core to the outside layer, forming the "Tempered Martensite" structure.
Atmospheric cooling
The austenitic core of the TMT bars transforms into a ferrite-pearlite structure that involves placing the bars on a cooling bed and arranging them to cool at room temperature. This process ensures that the bar's tensile strength improves its weldability.
Bottom Line
The manufacturing process of the TMT bar plays a key to attaining the best quality TMT bar. TMT bar manufactured at integrated manufacturing plants has better quality over scrapped metal TMT bars. Companies like SEL Tiger TMT, SRMB, and Tata Tiscon where you can be assured the quality standards meet and exceed expectations.
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