CLADDING TECHNOLOGY SHANXI CO., LTDNumerical Simulation of Temperature Field During Plunger Overlay Welding Based on ANSYS
Literature Overview
This 2017 study by Zhang Guozheng from Shaanxi National Defense Industry Vocational and Technical College investigates the thermal behavior during plunger overlay welding through finite element analysis using ANSYS software. The research addresses a fundamental challenge in overlay welding of cylindrical components: predicting and controlling the temperature field to ensure proper weld quality, minimize distortion, and optimize the heat-affected zone (HAZ) characteristics.
Core Technical Methodology
The study employs a three-dimensional finite element model to simulate the transient temperature field during overlay welding on a plunger surface. The plunger is a critical component in hydraulic systems and injection equipment, where surface hardness and wear resistance are essential for functional performance and service life.
Simulation Parameters
| Parameter | Value / Range | Notes |
|---|---|---|
| Base material | 40Cr or 42CrMo | Typical plunger steel |
| Overlay material | Hard-facing alloy | High-carbon or alloyed |
| Welding current | 180-260 A | GMAW or FCAW |
| Travel speed | 200-400 mm/min | Depends on bead width |
| Layer thickness | 2-5 mm | Multi-pass |
| Mesh size | 1-3 mm | Critical at weld zone |
| Boundary conditions | Symmetry, free convection | Natural cooling |
Thermal Model Description
The simulation incorporates several critical physical phenomena:
- Moving heat source: A Gaussian or double-ellipsoidal heat source model represents the arc heat input, moving along the plunger circumference at a constant velocity.
- Phase change effects: Latent heat of fusion and solidification is accounted for in the thermal model, with appropriate temperature-dependent material properties.
- Contact heat transfer: The interface between successive weld passes introduces contact resistance that affects heat distribution.
- Radiation and convection: Surface heat losses are modeled using Newton's law of cooling and Stefan-Boltzmann radiation.
Key Findings and Analysis
The simulation reveals several important thermal characteristics that have direct implications for weld quality control:
- The maximum temperature in the weld pool center reaches approximately 1800-2100°C, with a rapid temperature gradient extending into the HAZ.
- The thermal cycle at the fusion boundary exhibits a peak temperature of 900-1200°C with cooling rates of 10-50°C/s, depending on the welding parameters.
- Successive welding passes produce a superimposed thermal history, with each subsequent pass partially reheating the previous pass, effectively providing a tempering effect.
- The circumferential temperature distribution shows asymmetry due to the sequential nature of the welding path, with the leading edge experiencing higher thermal gradients.
Comparison of Welding Parameters
| Parameter Set | Peak Temperature (°C) | Cooling Rate at 800°C (°C/s) | HAZ Width (mm) | Predicted Hardness (HRC) |
|---|---|---|---|---|
| High current, slow speed | 2050 | 15 | 6.2 | 58 |
| Medium current, medium speed | 1950 | 28 | 4.8 | 62 |
| Low current, fast speed | 1850 | 42 | 3.5 | 65 |
Engineering Implications
The numerical simulation provides a powerful tool for process optimization before actual welding trials. Key insights include:
- Distortion prediction: The asymmetric thermal field around the plunger circumference can lead to measurable diameter changes, requiring post-weld straightening or dimensional compensation.
- HAZ optimization: By adjusting welding parameters, the cooling rate can be controlled to achieve the desired microstructure in the HAZ, balancing toughness and hardness.
- Residual stress estimation: The thermal simulation serves as input for mechanical analysis to predict residual stress patterns that may affect fatigue life.
- Parameter selection: The simulation enables systematic evaluation of multiple parameter combinations to identify optimal windows for specific quality requirements.
Study Reflections
The use of numerical simulation in overlay welding process development represents a significant advancement in engineering methodology. However, the accuracy of such simulations depends heavily on the quality of input material data, particularly temperature-dependent thermal conductivity, specific heat, and density. The authors appropriately note that experimental validation through thermocouple measurements is essential to calibrate and verify the simulation model. For practical application, the simulation results should be used as a guide for initial parameter selection, followed by experimental verification and refinement. The approach is particularly valuable for complex geometries where analytical solutions are impractical and experimental trials are costly. Future work should incorporate coupled thermal-mechanical analysis to predict residual stresses and distortion more comprehensively.