Simulação numérica das distorções e tensões residuais em chapas grossas submetidas ao resfriamento acelerado em função das contrações térmicas

Abstract

The steel plates must meet the most rigorous standards and needs market. For this, in the lamination the steel is subjected to thermomechanical processes aiming at obtaining surface qualities, shape, dimensions and mechanical properties compatible with the requirements of its application. A process increasingly used to obtain these characteristics is the accelerated cooling where high cooling rates are used to allow the grain refinement and obtaining microstructures consisting of bainite, martensite and ferrite. On the other hand, when cooling does not occur in a homogeneous manner, undesirable characteristics are generated in the plates such as residual stresses and distortions, characterized by shape defects such as buckling, camber and gutter. These characteristics are reasons for the scrapping or reworking that generate increase of the lead-time and the costs of production. Computational simulations to model and predict the occurrence of these defects are intensely used in academia and industry. The prediction allows increase the control process variables, product performance, and decrease costs and rework. The objective of this work was numerically simulate the accelerated cooling process in steel plates, distortions and residual stresses, evaluating the influence of the non-homogeneous cooling rate on the two faces of the plate or along its width or length. For this purpose, the Finite Element Method was used to perform 2D simulations. The steel used was AISI 1015 available from the DEFORMTM software version 10.0 library. In this work, the influence of the phase transformations wasn’t evaluated and, therefore, the missing of alloying elements in the steel is irrelevant. The results have showed a strong influence of non - uniform accelerated cooling on the generation of residual stresses and distortions. Additionally, a strong relationship was observed between the distribution of the non-uniformity of the cooling and the type of shape defect obtained.