Influência das variáveis do resfriamento acelerado na microestrutura e na planicidade de chapas grossas de aço da classe API

Abstract

TMCP (Thermo Mechanical Control Process) is a technology that combines controlled rolling with accelerated cooling for production of heavy plates of steels for various applications, including those for oil and gas transportation, meeting the API standards. There are several benefits in terms of quality and productivity associated to use of this technology, but a point of concern is related to flatness requirements, because the intense cooling applied in the process may cause large temperature heterogeneity in the plate. This, in turn, may lead to unacceptable flatness problems, as the intense cooling covers the transformation temperature range. As such, this work focused on the effect of different accelerated cooling strategies on mechanical properties and flatness of API X70 grade steel plates. Based on numerical simulations of different strategies, the resulting cooling curves were determined and used for process simulations by dilatometry, aiming at checking the feasibility of doing industrial experiences. Thus, experimental lots of plates were produced using five selected cooling strategies that were simulated. The results of microstructure, tensile properties, hardness and flatness were evaluated in the plates produced, allowing for the determination of the best cooling strategies that favored the best combination between mechanical properties and flatness, complying with the API standard.