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ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
An In-House Finite Volume Analysis to Predict the Heat Affected Zone in TIG Welding
Submission Author:
João Rodrigo Andrade , MG , Brazil
Co-Authors:
Stephanie Loi Brião, João Rodrigo Andrade, Fran Lobato, Luiz Eduardo dos Santos Paes, Louriel Vilarinho, Ruham Reis
Presenter: João Rodrigo Andrade
doi://10.26678/ABCM.ENCIT2020.CIT20-0178
Abstract
The Heat Affected Zone (HAZ) is considered the most relevant region of a weld bead, due to the presence of brittle phases and grain growth. By definition, the HAZ was submitted to temperatures below melting, but sufficient to cause microstructural changes. Experimentally, it is possible to identify microstructure modifications through chemical etching or measurement of hardness profile. However, there is not a criterion for HAZ boundaries based on a thermal profile resultant from the numerical simulation. Usually, the critical temperature ($T_c$) is adopted. For carbon steels, this temperature is $727~^\circ$C, where austenitization starts. The present paper proposes to consider the austenite phase fraction ($f$) from transformation kinetics besides this temperature, through the modified Johnson–Mehl–Avrami (JMA) equation. To investigate that, an “in-house” MATLAB-based code was developed, using the Finite Volume Method and validated experimentally for an autogenous Tungsten Inert Gas (TIG) process. The results pointed that the austenite phase fraction can be used with the critical temperature to delimit the HAZ considering the value of $1\%$ of austenitization as the start value, but there is not a significant difference in practice ($0.01$ mm) when using only the critical temperature criterion. Therefore, the implementation of the JMA equation in a numerical model is more relevant to identify the regions subjected to a higher degree of phase transformation, and the consequently higher probability of brittle phases, than to delimit the HAZ boundaries.
Keywords
GTAW, Finite Volume, Simulation, temperature field, Phase Transformation
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