Microstructural and Mechanical Characterization of Autogenous GTAW Weld in High-Manganese Austenitic Steel Ti-Containing

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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.10





Microstructural and Mechanical Characterization of Autogenous GTAW Weld in High-Manganese Austenitic Steel Ti-Containing with Thermal Analysis V. García-García1, I. Mejía1, F. Reyes-Calderón2 1 Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U-5” Ciudad Universitaria, 58066 Morelia, Michoacán, México. Email: [email protected], [email protected]

2 Departamento de Metalmecánica, Instituto Tecnológico de Morelia, Av. Tecnológico 1500, 58120 Morelia, Michoacán, México.

ABSTRACT

The welding heat input has been pointed out as a main limiting factor for TWinnig Induced Plasticity (TWIP) steel weldability. Scarce research works have been focused on the study of application and effects of the Gas Tungsten Arc Welding (GTAW) process in the TWIP steel, especially in higher thickness plate. In this research work was conducted a detailed analysis of a butt weld joint performed in plates of TWIP steel microalloyed with titanium (TWIP-Ti) of 6.3 mm thickness. The autogenous GTAW process with low heat input was applied. The analysis considered grain size measurements, second phases identification, post-weld mechanical properties (microhardness) and the welding thermal field. A Finite Element Model (FEM), validated through experimental results, allowed correlating metallurgical results with the thermal field. Likewise, the phases prediction carried out by means of JMatPro 9.0 software during solidification process as well as the estimation of particle precipitation were in good agreement with the experimental results. These predictive diagrams were calculated taking into account the TWIP-Ti steel chemical composition, the grain size measured in critical weld regions and experimental cooling rates. The low heat input improved the microstructural conditions in the heat affected zone (HAZ) whose average grain size and precipitate particles, like (C, N)Ti, promoted good mechanical properties as compared to the base material (as-solution condition). Some particles like Al2O3 y MnS produced microporosities in the HAZ. Despite this, the weld joint did not present hot cracking in the FZ-HAZ interface.

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INTRODUCTION Twining Induced Plasticity (TWIP) steel exhibits a high strain hardening and impact absorption energy as well as high ductility derived from its austenitic microstructure [1]. The above had positioned the TWIP steel as an interesting alternative for the automotive industry with the aim to enhance the vehicle strength/weight ratio [23]. Nevertheless, TWIP steel processing, particularly the welding process, brought about a variety of undesirable effects. It is well-known that welding heat input affects the chemical composition (dilution and segregation), g