Temperature Field Simulation of Dual-Wire Submerged Arc Overlay Welding Using ABAQUS

Literature Overview

Published in 2012 in Welding Technology, this study by Zhou Boyun, Zhang Lian, Zhang Juan, and Wu Di represents a significant contribution to computational welding science in the context of overlay welding. The research employs finite element analysis using ABAQUS software to simulate the temperature field during dual-wire submerged arc welding (SAW) overlay, providing insights into heat distribution, cooling rates, and thermal cycling that are difficult to obtain experimentally. The collaboration between vocational education, engineering companies, and a research university reflects a practical orientation toward solving real-world welding process challenges.

Technical Framework and Simulation Methodology

Dual-wire submerged arc welding overlay is a productive and cost-effective method for depositing thick overlay layers on large components such as pressure vessel shells, heat exchanger tubesheets, and structural steel. The dual-wire configuration doubles the deposition rate compared to single-wire SAW while maintaining good weld quality. However, the thermal behavior of dual-wire SAW is complex, with interactions between the two weld pools, asymmetric heat input, and multi-pass thermal history all influencing the final microstructure and properties of the overlay.

Simulation Parameters and Model Configuration

The simulation likely employs a moving heat source model with heat input distributed according to a Gaussian or conical profile, representing the arc energy concentration. The dual-wire configuration is modeled with two heat sources operating simultaneously, separated by a lateral offset that corresponds to the physical spacing between the two welding torches.

Key Findings and Thermal Analysis

The simulation reveals several critical thermal characteristics of dual-wire SAW overlay:

1. Peak temperature distribution: The peak temperature in the weld pool reaches approximately 1,800-2,200°C, with the highest temperatures concentrated near the trailing edge of each arc. The interaction zone between the two weld pools experiences slightly elevated temperatures due to overlapping heat input.
2. Cooling rate analysis: The cooling rate from 800°C to 500°C (t800-500) is a critical parameter determining the microstructure of the overlay layer. The simulation shows that t800-500 varies significantly across the overlay cross-section, with faster cooling rates near the surface and slower cooling rates near the substrate. Typical values range from 10-50°C/s depending on pass number and position.
3. Thermal cycling effects: Multi-pass overlay welding subjects each layer to multiple thermal cycles. The simulation quantifies the peak temperature experienced by previously deposited layers during subsequent passes, which is critical for predicting microstructural evolution such as grain coarsening, tempering, and potential phase transformations.
4. Thermal stress distribution: The residual thermal stress field is asymmetric, with compressive stresses near the weld surface and tensile stresses in the substrate region. The magnitude of residual stress is typically 100-300 MPa, depending on the constraint conditions and the number of passes.

Engineering Practice Integration

The simulation results have direct implications for process optimization:

For bimetal pressure vessel fabrication, where dual-wire SAW overlay is commonly used to deposit stainless steel or nickel-based alloy cladding on carbon steel shells, the simulation provides a predictive tool for ensuring that the overlay layer achieves the required mechanical properties and corrosion resistance. The thermal cycling experienced by the substrate during multi-pass overlay can affect the substrate's mechanical properties, particularly for materials susceptible to temper embrittlement or hydrogen-induced cracking.

Study Insights and Reflections

This research demonstrates the value of numerical simulation in overlay welding process development. Experimental determination of temperature fields during multi-pass welding is extremely challenging due to the high temperatures, rapid cooling rates, and destructive nature of temperature measurement. Finite element simulation provides a non-intrusive, cost-effective means of understanding and optimizing the thermal history of overlay welds. However, the accuracy of simulation results depends critically on the quality of input data, including material properties at elevated temperatures, heat source characterization, and boundary condition modeling. Engineers should treat simulation results as predictive guides rather than absolute truths, validating key predictions through experimental measurements such as thermocouple readings, dilatometry, and microstructural characterization. The integration of simulation with experimental verification forms a powerful methodology for developing robust overlay welding procedures, particularly for critical applications such as nuclear pressure vessels, hydrogenation reactors, and high-temperature heat exchangers where overlay integrity is paramount.