Thermex quenching is a game changing technology that has revolutionized the Indian steel production industry. The introduction of the concept of quenching and self-tempering rebars, ended the standard Indian practice of using Cold Twisted Deformed bars among top steel bar manufacturers in the country. On account of its simplicity, low-cost, ease in operation and capability of producing high strength deformed bars, Thermex QST Technology gained immediate global acceptance.

The Thermex process was developed and branded by Germany engineering firm Hennigsdorfer Stahl Engineering (HSE) in the 1970s. South India’s top TMT bar manufacturer Pulkit Metals Private Limited and Pushpit Steels Private Limited have been granted license rights from HSE to use the Thermex quenching system

What exactly is Thermex Quenching?

Thermex QST (quenching and self tempering) technology imparts a short, intensive but very precise in line quenching of the rolled bar resulting in a hardened periphery through a proprietary system. On further cooling of the bar in atmosphere, a thermal exchange (THERMEX) occurs between the core and the cooled martensite surface outside .The resultant bar structure is a distinct tempered martensite at periphery and a fine grained ferrite-pearlite structure in the central zone.

The quenching process implemented by TMT bar manufacturers, comes with the capability of producing a high strength bar from comparatively inexpensive low carbon steel.  Quenching and tempering processes strengthen materials like steel and other iron-based alloys. These processes strengthen the alloys through heating the material while simultaneously cooling in water, oil, forced air, or gases such as nitrogen.

In this process known as quenching or quench hardening, steel is thermally heated above the critical (austenitic) temperature. Rapid cooling is then effected whereby the change from austenite to pearlite is suppressed to form instead a material called martensite as the outer layer which is responsible for the hardness of the quenched steel. Martensite has a changeable microstructure and the material may then be tempered at various lower temperatures to the desired hardness. Quenching and tempering produces tougher steel and eliminates the need for post heat treat straightening and stress relieve.

The Thermex quenching edge:

  • The Quenched and Tempered bars have a martensitic layer of the outer surface that enables retention of strength in case of fire hazards and situations where temperatures rise upto 600°C.
  • The Quenched bars have external ribs running across the entire length of them that gives superior bonding strength between the bar and concrete. It can give up to 20% more strength to concrete structures with the same quantity of steel. 
  • The Thermex Quenched bars have a soft ferrite-pearlite core that enables the bar to bear dynamic and seismic loading, making it earthquake resistant. This makes them the favourite product of steel bar manufacturers. 
  • Quenched and Tempered TMT bars withstand bending and rebending, due to lower carbon content and higher elongation. This property makes these bars easier to work with. 
  • Thermex Quenching makes the bars safe and economical, due to the bendability, weldability and excellent ductility it lends to the products, allowing features like butt welding and lap-welding. 
  • The Thermex Quenching process gives the bar anti-corrosive properties. They resist corrosion better than cold, twisted and deformed (CTD) bars. As there is no twisting process during TMT, no torsional stress occurs, and in the absence of torsional stress, surface defects are avoided in TMT bars.

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