Zhuojin Pipe Fitting Co., LtdTemperature Field Simulation of MIG-Based Arc Additive Manufacturing with Different Interlayer Dwell Times
Literature Overview
This paper by Zhang Tianlei, Xu Gang, Shen Yantao, Ming Can, He Linji, and Ma Chunwei, published in Light Industry Machinery in 2020 (Vol. 38, No. 3, pp. 37-42), investigates the temperature field characteristics of arc additive manufacturing (AM) based on MIG welding, with particular focus on the effect of interlayer dwell time. The research was supported by the Shanghai University of Engineering Science Graduate Research Innovation Project (18KY0514) and conducted at Shanghai University of Engineering Science and Beijing Haiji Technology Development Co., Ltd.
Core Technical Approach
The study employed ABAQUS finite element software to establish a three-dimensional transient thermal simulation model of the arc additive manufacturing process. The model was validated against experimental measurements obtained using an infrared thermometer during the actual AM process. The key simulation parameters included:
| Parameter | Value/Range | Description |
|---|---|---|
| Heat source model | Moving double-ellipse (Goldak) | Represents MIG arc heat distribution |
| Thermal conductivity | Temperature-dependent | Al alloy properties |
| Specific heat | Temperature-dependent | Accounts for latent heat of fusion |
| Convection coefficient | 10-50 W/(m²·K) | Surface cooling |
| Radiation coefficient | 5.67×10⁻⁸ W/(m²·K⁴) | Stefan-Boltzmann |
| Interlayer dwell time | 0-300 s | Variable parameter |
| Layer thickness | 2-3 mm | Typical AM layer |
| Deposition rate | 500-1000 mm/min | Travel speed |
Key Findings and Analysis
The simulation results revealed several important characteristics of the temperature field in MIG-based arc AM:
- Progressive thermal accumulation: As the number of deposited layers increases, the high-temperature region of the workpiece gradually expands. This thermal accumulation effect is a fundamental challenge in AM, as it leads to increased residual stresses and potential distortion.
- Effect of interlayer dwell time: Increasing the interlayer dwell time reduces the high-temperature region, allowing more heat to dissipate before the next layer is deposited. This is a critical process parameter for controlling the thermal history of the AM part.
- Model validation: The simulated temperature curves showed good agreement with the experimentally measured thermal cycles, validating the accuracy of the finite element model and the assumed heat source parameters.
- Metallurgical bonding: The study confirmed that MIG-based arc AM achieves good metallurgical bonding between layers, which is essential for the mechanical integrity of the AM part.
Thermal Cycle Analysis
The thermal cycle in arc AM is characterized by repeated heating and cooling events, each corresponding to a single layer deposition. The key thermal cycle parameters include:
| Parameter | Typical Value | Engineering Significance |
|---|---|---|
| Peak temperature | 600-900 °C | Determines microstructure evolution |
| Cooling rate | 10-100 °C/s | Affects grain size and precipitate formation |
| Time above 400 °C | 5-30 s per layer | Influences phase transformation |
| Interlayer temperature | 150-400 °C | Critical for bonding quality |
| Thermal gradient | 50-200 °C/mm | Drives residual stress formation |
The interlayer dwell time directly controls the interlayer temperature, which in turn affects:
- The degree of re-melting of the previous layer during deposition of the new layer
- The grain structure evolution (columnar vs. equiaxed grains)
- The residual stress distribution within the AM part
- The risk of cracking in the weld overlay
Application to Pipe and Fitting Repair
Arc additive manufacturing based on MIG welding has significant applications in pipe and fitting repair and fabrication:
- Pipe repair: Localized repair of corrosion damage or mechanical defects on in-service pipes, where the interlayer dwell time must be carefully controlled to minimize thermal distortion of the existing pipe geometry.
- Fitting fabrication: Additive manufacturing of custom pipe fittings (elbows, tees, reducers) where the thermal accumulation effect must be managed to ensure dimensional accuracy.
- Overlay welding: Deposition of corrosion-resistant or wear-resistant alloys on pipe surfaces, where the interlayer temperature must be controlled to ensure proper bonding between the overlay and the base material.
Process Optimization Strategy
Based on the findings of this study, a systematic approach to optimizing the interlayer dwell time can be developed:
- Determine the minimum interlayer temperature: Below this temperature, bonding quality deteriorates due to insufficient re-melting of the previous layer.
- Determine the maximum interlayer temperature: Above this temperature, excessive thermal accumulation leads to grain coarsening and increased residual stresses.
- Calculate the required dwell time: Using the validated thermal model, calculate the dwell time needed to bring the interlayer temperature within the target range.
- Implement adaptive control: In automated AM systems, use real-time temperature monitoring to adjust the dwell time dynamically based on the actual thermal state of the workpiece.
Key Questions and Reflections
A critical question arising from this study is the optimal balance between productivity and quality. Shorter interlayer dwell times increase the deposition rate but risk thermal accumulation and quality degradation. Longer dwell times improve quality but reduce productivity. The optimal dwell time depends on the specific material, geometry, and quality requirements of the AM part.
Another consideration is the scalability of the simulation approach. The three-dimensional transient thermal model used in this study is computationally intensive, and simulating large AM parts (such as full-scale pipe sections) may require significant computational resources. For industrial applications, reduced-order models or hybrid simulation-experiment approaches may be more practical.
Study Insights and Implications
This paper provides valuable insights into the thermal management of MIG-based arc additive manufacturing. The validated thermal model and the systematic study of interlayer dwell time effects offer a practical tool for process optimization. For pipe and fitting manufacturers exploring additive manufacturing for repair and fabrication applications, the key takeaway is that thermal management—particularly through controlled interlayer dwell times—is essential for achieving consistent quality. The good agreement between simulation and experiment also demonstrates that finite element analysis can be a reliable tool for process development and optimization, reducing the need for extensive trial-and-error experimentation.