How to choose Authentic TMT Bars
The iconic Re-bar, which created a ripple in the infrastructure industry, started its historic journey from M S Rounds. Later, it evolved into the Cold Twist Deformed Bars and then the TMT bars which revolutionized the construction business. Today, numerous brands in the market offer TMT bars. But before you make a choice, ensured that the TMT bars or Thermo Mechanical Treated bars are really what they claim to be. What makes TMT bars much sought after is its unique benefits. Every step of the manufacturing process has to be done according to scientific regulations with utmost precision. But the hard truth is many rolling mills do not follow these procedures strictly, and because of that the unique benefits that these steel bars hold are lost. To ensure the grade, quality, strength, rib, section weight, and stability of TMT bars remain consistent, the latest updated technology should be adopted and stringent quality and standard checks should be in place during the process.
One of the basic factors involved in the Thermo Mechanical Treatment is ensuring the use of good quality raw materials. Pure steel billets should be used for manufacturing the bars and can be sourced from pioneers in the field like SAIL (Steel Authority of India Limited) and Vizag whose formulas for mixtures are scientifically accurate. Many choose to use steel melted from scrap (incoat) as the raw material. The bars which are manufactured thus will neither have the strength nor benefits a TMT bar should have.
During the initial stage of Thermo Mechanical Treatment, the fully automated furnace which ensures high energy efficiency, controlled firing, and controlled affluent release are used to push forth the steel billets pre-set to a certain temperature. The most important factor in this step is to make sure the temperature of the billet is 1200 degrees centigrade. Only billets that are uniformly heated up and passed through 21 to 25 times will allow for precise reduction. This is achieved by filling the furnace with furnace oil which has a higher calorific value than its counterparts. But many rolling mills use coal to heat the furnace instead which will heat up to a maximum temperature of 900 degrees centigrade. This makes the treatment process incomplete and also remains a cause of environmental damage.
After completing stage one, the billets with a 1200 degree centigrade temperature, is passed through the P L C controlled automated high-speed rolling mills. This high-speed rolling mill ensures that the temperature of the billets is constant and 21 to 25 passes are done. Thus the billets take the shape and strength of TMT bars within 40 seconds. Since many rolling mills have a manual processing method, the average time taken exceeds two minutes. The strength is also compromised in such a case because of the temperature of the billets becomes unstable. To reduce the processing time, the rolling mills even reduce the number of passes to 10 – 15, which makes the bars weak.
The bars that come out of proper processing methods will have a temperature of 400 – 450 degrees centigrade. The hot bars are passed through quenching boxes, aided with a computerized system that helps in the controlled cooling of these bars. The outer layer of these bars is strengthened, the Martensite reaches the required state, and Austenitic remains static after this process.
The bars that come out after the quenching process is of around 300 degrees centigrade, can be cut to pre-determined lengths and sizes, and then sent to an automatic cooling bed. It stays without contact with each other or outside contact for about 5 – 8 minutes adjusting to the normal temperature. The most advanced cooling beds ensure zero contact and prevent the side-effects of contact, making it retain all the benefits of TMT bars. The manual processing meanwhile is done by dragging the bars using hooks which may affect the shape and strength adversely. Automatic cooling beds not only ensure the benefits of TMT are retained but also the safety of the workers.
The steel billets that undergo the proper processing is monitored continuously by computers to maintain the quality level at all times. This makes the bars bendable to the required shape but not make it brittle. It can be welded easily and can even withstand the adversities caused by earthquakes. Many leading brands manufacture the TMT bars as coils first, which can be de-coiled and cut to the required size later in the market. But this may lead to loss of quality of these bars.
TMT bars should be a strong product that lasts generations. So, while choosing TMT bars, one has to be extremely careful. It is very important to purchase TMT bars that are made from the best raw materials, with the latest technology, correct procedures, and stringent quality checks.