FEM-thermodynamic simulation methodology to predict the influence of t_8/5 on the coarse grain heat-affected zone of a Cr-Mo low-alloy steel pipe

This work aimed to develop a microstructure-predicting methodology (MPM) using coupled physical-FEMthermodynamic simulation to predict the influence of cooling time from 800 to 500 degrees C (t(8/5) - 15, 30, 80, and 210 s) on the microstructure and mechanical behavior of the coarse grain heat-affected zone (CGHAZ) of a Cr-Mo low alloy steel welded joint. The MPM was experimentally validated. The MPM certainly predicted that the increase of t(8/5) caused a remarkable change in CGHAZ microstructure (martensite and bainite to ferrite with aligned and non-aligned martensite-austenite-carbide M-A-C) and also decreases the Vickers microhardness. The MPM and experimental data show that the use of welding parameters that increases t(8/5) (reducing the cooling rate) can jeopardize the welded joint behavior. Besides, the MPM proved to be a suitable tool for estimating the microstructure and microhardness of the CGHAZ.