THERMEX –THE QST REBAR TECHNOLOGY
Hennigsdorfer Stahl Engineering GmbH (HSE) Germany developed, after years of research and field trials, a unique Quenching and Self-tempering (QST) process that allowed rolling mills to produce high strength deformed bars which fully met the demands of civil engineers of different countries, at a lower cost (without the use of costly alloys). This basic process and subsequent improvements were patented worldwide. THERMEX is the registered trademark of HSE Germany who has allowed H&K India to own it in the Indian Region. STEELMAX TMX uses the QST rebar technology and therefore owns TMX (THERMEX) license to use the mark on the product. Each Thermex System is specifically designed to suit individual mill parameters and the rebar properties desired by the client. Thermex Systems can be offered to meet any of the main and popular international specifications besides any special requirements.
THERMEX/TMX steel rebars– All rebars that are produced through the Thermex system of HSE, Germany are called THERMEX rebars. TMX is an acronym for THERMEX. THERMEX is the brand name referring to the Quenching & Self-tempering process. It is a Licensed Technology & System obtained by more than 300 mills in India and overseas. So, TMX rebar is a specific brand of rebar.
TMX VS TMT
All TMX steel rebars are TMT rebars, but all TMT rebars are not THERMEX/TMX rebars. Only those TMT bars manufactured using the licensed QST technology are TMX or THERMEX rebars. The structural uniformity is the highlight feature of TMX Bars.THERMEX process converts the bar surface to a hardened structure. The subsequent phase involves cooling at ambient temperature to allow the hot core to temper the surface through the Thermex exchange. This results in a unique structure of tempered martensite periphery and fine-grained ferrite-pearlite at the core. This structure should be uniform throughout the cross-section of rebars.
MICROSTRUCTURE OF BARS
Pearlite is a lamellar aggregate of ferrite and cementite. It is a result of the eutectoid reaction which takes place when a plain carbon is cooled slowly from the temperature range at which austenite is stable.
Bainite is a decomposition of austenite consisting of an aggregate of ferrite and carbide. Its appearance is feather-like if formed in the upper part of the temperature range and acicular if formed in the lower part.
It is formed by the rapid cooling of Austenite. Martensite is not shown in the equilibrium phase diagram of the Iron- Carbon system because it is a metastable phase, the kinetic product of rapid cooling of steel containing sufficient carbon.