Dynamic Simulation of Temperature Field in Dissimilar Material Cladding Based on ANSYS

Literature Overview and Research Background

This study presents a finite element analysis (FEA) approach using ANSYS software to simulate the dynamic temperature field during dissimilar material cladding welding. Dissimilar material cladding—such as stainless steel on carbon steel or nickel alloy on carbon steel—presents unique thermal and metallurgical challenges due to the large differences in thermal conductivity, specific heat, and thermal expansion coefficients between the base material and the cladding material. The study aims to provide a predictive tool for optimizing welding parameters and understanding the thermal history of the cladding process.

Core Technical Content

The simulation employs a three-dimensional transient thermal analysis model that accounts for the moving heat source, heat conduction, convection, and radiation losses. The heat source is modeled using a double-ellipsoidal Gaussian distribution, which is widely accepted for representing the energy distribution in arc welding processes. The model is validated against experimental thermocouple measurements to ensure accuracy.

Model Parameters and Assumptions

Thermal Field Analysis Results

The simulation results show that the peak temperature in the weld zone reaches approximately 1800–2200°C, with a rapid decrease in temperature away from the weld center. The thermal gradient at the interface between the base material and the cladding layer is a critical parameter, as it determines the cooling rate and consequently the microstructure and mechanical properties of the weld metal and heat-affected zone (HAZ).

The simulation reveals that the cooling rate (measured as the time interval between 800°C and 500°C) varies significantly across the weld cross-section. The center of the weld pool experiences the highest cooling rate (approximately 50–100°C/s), while the HAZ experiences a lower cooling rate (approximately 5–20°C/s). This variation in cooling rate leads to a gradient in microstructure from the weld center to the base material, which must be carefully managed to ensure adequate toughness and resistance to cracking.

Effect of Welding Parameters on Thermal Field

The study systematically varies the welding current, voltage, and travel speed to determine their effects on the thermal field. Increasing the welding current increases the peak temperature and the width of the high-temperature zone, while increasing the travel speed reduces the heat input and the cooling rate. The optimal combination of parameters is identified as that which provides adequate fusion and dilution control while minimizing the thermal gradient at the interface.

Validation and Comparison with Experimental Data

The simulation results are validated against experimental thermocouple measurements taken at various locations around the weld. The agreement between simulated and measured temperatures is generally within ±50°C, which is considered acceptable for engineering applications. The validation confirms the reliability of the model for predicting thermal history and optimizing welding parameters.

Engineering Practice Integration

In pressure vessel fabrication, dissimilar material cladding is commonly used to provide corrosion resistance while maintaining the mechanical strength of carbon steel. The thermal simulation provides valuable guidance for welding procedure specification (WPS) development, particularly in determining the optimal preheat temperature, interpass temperature, and welding parameters for different cladding configurations.

A critical application of this simulation is in predicting the risk of cracking in the HAZ and weld metal. High cooling rates in the HAZ can lead to the formation of hard, brittle microstructures such as martensite, which are susceptible to hydrogen-induced cracking. The simulation can identify regions where the cooling rate exceeds critical thresholds and suggest modifications to the welding procedure to mitigate this risk.

Key Questions and Reflections

A significant question is the accuracy of the thermal simulation in predicting the metallurgical transformations that occur during welding. While the thermal field is accurately simulated, the prediction of microstructure and mechanical properties requires additional models that account for phase transformations, precipitation, and grain growth. The integration of thermal simulation with metallurgical models (such as JMatPro or Olena) could provide a more comprehensive predictive tool for cladding welding optimization.

Another reflection concerns the scalability of the simulation to complex geometries. While the simulation is accurate for simple flat plate cladding, the application to curved surfaces, thick sections, and multi-pass welding requires additional computational resources and model complexity. The development of simplified models or surrogate models could facilitate the application of thermal simulation to practical engineering problems.

Study Insights and Implications

This research demonstrates the value of thermal simulation in optimizing dissimilar material cladding welding procedures. The key insight is that the thermal field is a critical determinant of weld quality, and its prediction through simulation provides a powerful tool for welding procedure development and optimization. For engineering practice, this study provides a framework for integrating thermal simulation into the welding procedure qualification process, enabling more efficient and reliable development of welding procedures for dissimilar material cladding applications in pressure vessel fabrication and other heavy industry sectors.