Effect of the Heat Input on the Heat Affected Zone in the Austenitic Stainless Steel Welding by the GTAW Process-An Expe
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Effect of the Heat Input on the Heat Affected Zone in the Austenitic Stainless Steel Welding by the GTAW Process-An Experimental and Computational Analysis V. García-García1, H. Hernández-Belmontes1, I. Mejía1, F. Reyes-Calderón2, C. Maldonado1 1
Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U-5” Ciudad Universitaria, 58066 Morelia, Michoacán, México. E-mail: [email protected], 2 [email protected] Departamento de Metalmecánica, Instituto Tecnológico de Morelia, Av. Tecnológico 1500, 58120 Morelia, Michoacán, México.
ABSTRACT
Arc welding processes such Gas Tungsten (GTAW), Gas Metal (GMAW) and Submerged Arc (SAW) are typically used in order to produce a weld joint in stainless steels (SS). However, welding thermal cycle generates a sensitization by formation of chromium carbides. In addition, the heat affected zone (HAZ) is also susceptible to sensitization and fracture of the weldment. Weld bead geometric parameters such depth penetration, fusion zone (FZ) width and size of HAZ are mainly determined by welding operation parameters. This research work studies the influence of welding current, welding speed and arc gap on the width and grain size in the HAZ produced by a single pass of autogenous GTAW process applied to a plate butt-welded joint of AISI 304 SS. The welded specimens were prepared for analysis by light optical (LOM) and scanning electron (SEM) microscopies to identify the interfaces between FZ-HAZ and base material as well as the grain growth in the HAZ. Adams equation for 2-D heat distribution was used to estimate theoretically the width of the HAZ. Furthermore, computational simulation which solved a convective-diffusion problem of the volumetric heat applied during the weld pool formation allowed to correlate the thermal gradient and the molten material flow of the FZ with the welding depth penetration, and width and grain size in the HAZ. The results demonstrated that the high heat input generates an important grain growth in the HAZ caused by low heat diffusion in the adjacent material to the fusion line. Welding speed was the main factor in the thermal gradient changes. Simulation results indicate that outward recirculating flow in the molten metal produced by surface tension forces is responsible for the shallow penetration of the autogenous GTAW process. Theoretical and computational estimations of the HAZ are in good agreement with the experimental results.
INTRODUCTION Downloaded from https://www.cambridge.org/core. Teachers College Library - Columbia University, on 30 Nov 2017 at 09:54:38, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2017.594
Due to the extended application of the GTAW process in welding of AISI 304 SS several researchers have studied the heat input effects in the material. Subodh et al. [1] demonstrated that heat input, grain growth and the extension of the heat affected zone (HAZ) have a direct relationship in the GTAW process. Unnikris
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