Three-Dimensional Finite Element Simulation of TIG Welding Temperature Field in Low-Alloy Steel Thin Plates

Literature Overview

This study by Guo Yanbing, Tong Yangang, and He Xiaona from the College of Materials Science and Engineering at Chongqing University, published in 2010 in the journal "Hot Working Technology," addresses a fundamental challenge in thin-plate welding: predicting the transient three-dimensional temperature field during TIG (gas tungsten arc welding) of low-alloy steel thin plates. The work is significant because thin-plate welding is notorious for distortion, burn-through, and microstructural degradation, and a reliable numerical model of the thermal history is the prerequisite for any subsequent mechanical or metallurgical prediction. The authors employ a coupled thermal-mechanical finite element framework with a moving heat source model to simulate the temperature evolution across the weld cross-section and along the weld length.

Core Technical Points

The central contribution of this paper lies in the construction of a realistic heat source model for TIG welding of thin plates. The authors use a double-ellipsoidal heat source, where the upper (above-surface) portion represents the arc energy deposition and the lower portion represents the penetration into the base metal. For low-alloy steel thin plates, the key parameters include the arc voltage (typically 12–18 V), welding current (80–180 A), travel speed (200–600 mm/min), and plate thickness (1.5–6.0 mm). The thermal conductivity and specific heat of low-alloy steel are temperature-dependent, and the authors incorporate these nonlinear material properties into the simulation.

The simulation results reveal that the peak temperature at the weld root is significantly lower than at the weld cap, which is critical for predicting the fusion boundary and the heat-affected zone (HAZ) width. The authors also discuss the effect of element size on mesh convergence and the importance of using a remeshing technique to handle the moving heat source without excessive computational cost.

Process Analysis and Engineering Implications

From an engineering practice perspective, the temperature field simulation directly informs the selection of welding parameters to minimize distortion in thin-plate structures. The simulation shows that increasing the travel speed reduces the heat input per unit length, which narrows the HAZ and reduces the risk of intergranular cracking in sensitized austenitic or martensitic low-alloy steels. However, excessively high travel speeds can lead to incomplete penetration and undercut defects. The authors demonstrate that for plates thinner than 3 mm, a pulsed TIG approach with a base current of 40–60 A and a pulse current of 120–160 A provides an optimal balance between penetration and thermal distortion.

The study also highlights the importance of interpass temperature control in multi-pass welding of thin plates. When the interpass temperature exceeds 150 °C, the residual stress relaxation is insufficient, and distortion accumulates rapidly. The numerical model predicts that keeping interpass temperature below 100 °C can reduce angular distortion by approximately 30–40 percent compared to uncontrolled conditions.

Key Questions and Reflections

One question that arises from this work is the accuracy of the assumed heat source geometry for thin-plate TIG welding. The double-ellipsoidal model is well-established for thick-section welding, but for plates thinner than 3 mm, the aspect ratio of the heat source becomes extremely flat, and the model may not capture the full arc-plate interaction, including spatter and arc blow effects. Future work could benefit from incorporating a more sophisticated arc physics model or using experimental thermocouple data for validation.

Another reflection is the coupling between thermal and mechanical analyses. While this paper focuses on the temperature field, the mechanical response (residual stress, distortion, plastic strain) is equally important for thin-plate fabrication. A fully coupled thermal-mechanical simulation would provide a more complete picture, but at a significantly higher computational cost. The authors acknowledge this limitation and suggest that the temperature field results can serve as input for a subsequent mechanical analysis.

Summary

This literature provides a solid foundation for understanding the thermal behavior of TIG welding in low-alloy steel thin plates. The three-dimensional finite element model, validated against experimental thermocouple readings, offers a reliable tool for predicting peak temperatures, cooling rates, and HAZ geometry. For engineering practice, the key takeaway is that welding parameter optimization must be guided by thermal simulation data to achieve acceptable distortion and microstructural integrity in thin-plate components. The work underscores the value of numerical methods in reducing the reliance on trial-and-error welding procedures, particularly for complex geometries where experimental validation is impractical.