Zhuojin Pipe Fitting Co., LtdNumerical Simulation of Overlay Welding Temperature Field for Hydraulic Support Piston Rod
Literature Overview
This paper, published in Hot Working Technology in 2021 by Zhang Jin, Zeng Wei, Chen Xiangyang, Wang Chengjun, and Hu Haixia from Anhui University of Science and Technology, presents a finite element analysis of the overlay welding process for hydraulic support cylinder piston rods. The study uses the ANSYS software platform with APDL programming and element birth-and-death techniques to perform transient thermal analysis under three preheating conditions: 20 degrees Celsius (ambient), 150 degrees Celsius, and 300 degrees Celsius. The research was funded by the Anhui Provincial Department of Education Natural Science Foundation Key Project (KJ2019A0127) and the Anhui Provincial Key Research and Development Program (201904a05020092).
Numerical Methodology and Modeling Approach
The numerical simulation employs a transient thermal analysis framework, which is appropriate for capturing the rapid heating and cooling cycles characteristic of overlay welding. The element birth-and-death technique is used to model the sequential deposition of weld layers, where each new layer is activated as the welding torch advances along the piston rod surface. This approach effectively simulates the progressive material addition without requiring remeshing, which is computationally efficient and physically representative.
The APDL (ANSYS Parametric Design Language) programming enables automated control of the thermal loading sequence, allowing the simulation to accurately replicate the multi-pass overlay welding process. The heat source model, while not explicitly detailed in the abstract, is critical for capturing the spatial and temporal distribution of thermal energy input. The three preheating conditions represent a practical range encountered in industrial practice, where ambient welding is common for small-scale repairs and preheating is applied for thicker sections or higher carbon equivalent materials.
Temperature Field Distribution and Preheating Effects
The simulation results reveal that the temperature field distribution is highly sensitive to the preheating temperature. At ambient temperature (20 degrees Celsius), the peak cooling rates in the weld zone are sufficiently high to promote the formation of quench-hardened microstructures, which are characterized by hard, brittle martensite that is susceptible to cracking. The thermal gradient between the weld zone and the surrounding base metal is steeper under ambient conditions, leading to higher thermal stresses and a greater tendency for cold cracking.
| Preheating Temperature | Peak Weld Temperature | Cooling Rate (Approx.) | Quench-Hardened Tendency |
|---|---|---|---|
| 20 degrees C (ambient) | High | Fast | High |
| 150 degrees C | Moderate | Moderate | Reduced |
| 300 degrees C | Lower peak gradient | Slow | Significantly reduced |
The preheating at 150 and 300 degrees Celsius reduces the thermal gradient between the weld and the base metal, thereby lowering the cooling rate and the tendency for quench-hardened microstructure formation. This is consistent with established welding metallurgy principles, where preheating is used to slow cooling rates, reduce residual stresses, and minimize hydrogen-induced cracking susceptibility.
Engineering Relevance for Hydraulic Support Components
Hydraulic support cylinder piston rods are critical components in underground mining equipment, where they are subjected to severe cyclic loading, abrasive wear, and corrosive environments. The overlay welding process is commonly used to restore worn piston rods or to add wear-resistant surface layers. The numerical simulation findings have direct practical implications:
- Preheating protocols: The simulation confirms that preheating to at least 150 degrees Celsius is beneficial for reducing quench-hardened microstructure, which should be incorporated into standard operating procedures for piston rod overlay welding.
- Post-weld heat treatment: Given the tendency for hard, brittle microstructures under ambient welding conditions, post-weld stress relief or tempering treatment is strongly recommended, particularly for high-strength piston rod materials.
- Multi-pass strategy: The element birth-and-death simulation approach validates the use of multi-pass welding strategies, where each subsequent pass provides a tempering effect on the previous pass, reducing overall hardness and brittleness.
Study Insights and Practical Recommendations
The value of this study lies in its quantitative prediction of thermal behavior under different preheating conditions, which provides engineers with a basis for process optimization without relying solely on trial-and-error experimentation. The simulation methodology using element birth-and-death technique is particularly relevant for overlay welding applications where the geometry changes progressively during the welding process. For practical implementation, engineers should consider combining numerical simulation with thermocouple-based temperature measurement to validate simulation predictions and refine heat source models for specific equipment and material combinations.