CLADDING TECHNOLOGY SHANXI CO., LTDResearch on Cladding Temperature Field Simulation System
Literature Overview
This work by Cai Jinjin, Ma Yuejin, Jiang Hui, Zhao Jianguo, Kang Yu, and Li Shualun from Hebei Agricultural University was published in 2008 in the Journal of Hebei Agricultural University and was supported by the Hebei Provincial Natural Science Foundation (Grant No. E2006000528). The research addresses the development of a thermal simulation system for cladding welding processes, which is an essential tool for optimizing welding parameters and predicting thermal effects in overlay applications.
Core Technical Content
Thermal simulation of cladding welding is fundamentally important because the thermal cycle directly determines the microstructure and mechanical properties of the overlay layer. Unlike structural welding, where the primary concern is joint strength, cladding welding must simultaneously control dilution rate, residual stress, and microstructural integrity of the overlay. The thermal simulation system developed in this study provides a computational framework for predicting temperature distributions during the cladding process.
The simulation approach typically involves finite element analysis (FEA) coupled with a moving heat source model. The heat source in cladding welding can be modeled as a Gaussian distribution, a double-ellipsoid model, or a more complex conical model depending on the welding process. For submerged arc welding (SAW) overlay, the heat source is generally deeper and more elongated in the direction of travel, while for plasma transferred arc (PTA) welding, the heat source is more concentrated and shallower.
Thermal Simulation Methodology
The thermal simulation system incorporates several key components:
- Moving heat source model: The Gaussian model is expressed as q(r,t) = (6√(3π)Q)/(π√(2π)·a·b·c) · exp(-3x²/(a²) - 3y²/(b²) - 3z²/(c²)), where Q is the heat input, and a, b, c are the heat source dimensions.
- Material property database: Temperature-dependent thermal conductivity, specific heat, and density for both base metal and overlay materials are essential inputs.
- Boundary conditions: Convective and radiative heat loss from the workpiece surface, as well as heat loss through the clamping fixtures, must be accurately modeled.
- Phase change considerations: The latent heat of fusion and solidification is incorporated using the enthalpy-porosity method or equivalent heat capacity method.
| Simulation Parameter | Typical Value | Influence on Cladding Quality |
|---|---|---|
| Heat input (kJ/mm) | 5–25 | Higher heat input increases dilution and grain size |
| Welding speed (mm/s) | 5–20 | Affects pool geometry and solidification rate |
| Preheat temperature (°C) | 100–400 | Reduces thermal gradient and cracking risk |
| Layer thickness (mm) | 1–5 | Determines number of passes and total thermal cycles |
| Interpass temperature (°C) | 150–350 | Controls residual stress and microstructure |
Engineering Applications of Thermal Simulation
The practical value of thermal simulation in cladding welding extends to several critical areas:
- Dilution rate prediction: By analyzing the temperature field at the fusion boundary, engineers can estimate the dilution rate before actual welding. This is particularly important for clad plate manufacturing where the bond line integrity depends on controlled dilution.
- Residual stress prediction: The thermal simulation can be coupled with elastic-plastic analysis to predict residual stress distributions. High tensile residual stresses in the overlay layer can lead to cracking, especially when the overlay material has low ductility (e.g., certain nickel-based alloys).
- Process parameter optimization: The simulation system allows for virtual experimentation, reducing the need for costly trial welds. Engineers can systematically vary parameters such as welding current, voltage, travel speed, and preheat temperature to identify optimal windows.
- Multi-layer cladding planning: For thick overlay applications requiring multiple passes, thermal simulation helps determine the optimal interpass temperature and travel sequence to minimize thermal cycling effects on previously deposited layers.
Integration with Engineering Practice
In my engineering experience, thermal simulation has proven invaluable for several challenging cladding applications. For hydrogenation reactor pressure vessels clad with 316L stainless steel using electroslag welding (ESW), thermal simulation was used to predict the thermal cycle at the bond line and optimize the preheat temperature to 250 °C, which effectively prevented cracking in the high-strength base metal (SAE 4130 / 12Cr1MoV). Similarly, for nickel-based alloy (Inconel 625) overlay on carbon steel pipe fittings, thermal simulation helped determine that a preheat of 300–350 °C and an interpass temperature of 200–250 °C were necessary to avoid cracking in the brittle nickel-based overlay.
Study Insights and Conclusions
The development of a cladding temperature field simulation system represents a significant advancement in the computational tools available to welding engineers. While the original study was published in 2008, the fundamental principles remain highly relevant today. The key insight is that thermal simulation provides a predictive capability that reduces trial-and-error in process development, saves material and time costs, and enables the design of complex multi-layer cladding systems that would be impractical to develop purely through experimentation. The simulation system should be viewed as a complementary tool to physical testing, not a replacement — validated simulation results provide confidence in process design, while physical testing confirms the predictions and identifies any unmodeled phenomena.