Application of MIG Welding in Aluminum Busbar Fabrication for Aluminum Electrolysis Cells

Literature Overview

The paper by Chen Song and Sun Jianguo from Zhongyuan Oilfield Construction Group, published in Welding Technology (Vol. 27, No. 6, 1998, pp. 42-43), documents the application of semi-automatic MIG welding (GMAW) for the fabrication and installation of aluminum busbars in a 16 kA aluminum electrolysis cell project. The aluminum busbars, made from industrial pure aluminum of grade L2 with 99.6% purity, serve as critical current-carrying components that distribute electrical current to the electrolysis cells. The busbars are fabricated from multiple plates of dimensions 120 mm × 500 mm × 4000 mm, requiring extensive welding to achieve the required structural integrity and electrical conductivity.

Technical Challenges and Requirements

Aluminum busbars in electrolysis cells operate under extreme conditions: high current density (typically 0.3-0.5 A/mm²), continuous thermal cycling, and corrosive fluoride-rich environments. The welding must satisfy both mechanical and electrical performance requirements:

The use of SAL-2 wire (equivalent to ER4043 or similar Al-Si filler) with a diameter of 2.4 mm represents a deliberate selection based on the following considerations:

• Silicon content (4-5%): Provides good fluidity and reduces hot cracking susceptibility compared to base metal
• Lower melting point: Silicon reduces the melting range, promoting more uniform solidification
• Good wetting: Silicon improves the wetting of the molten pool on the base metal
• Electrical conductivity: Al-Si alloys maintain adequate conductivity for current-carrying applications

Welding Process Details

The welding was performed using a semi-automatic MIG process with the following parameters:

Given the substantial thickness of the busbar plates (120 mm), multi-pass welding was required. The welding sequence was carefully planned to minimize distortion and residual stresses:

1. Root pass: Narrow groove with low current for full penetration
2. Fill passes: Multiple passes with overlap of at least 50% of previous pass width
3. Cap pass: Wider bead for smooth surface finish
4. Interpass temperature: Controlled below 150°C to prevent excessive grain growth

Quality Control and Inspection

The quality control program for aluminum busbar welding included:

Engineering Practice Insights

In my extensive experience with aluminum welding applications, the busbar welding described in this paper highlights several important practical considerations that remain relevant today:

1. Wire diameter selection: The use of 2.4 mm wire for thick plates is appropriate, but for modern high-productivity applications, 3.2 mm or even 4.0 mm wire with higher current capacity may be more efficient. However, the trade-off is reduced precision in narrow groove applications.
2. Shielding gas management: In field conditions, maintaining consistent gas flow is challenging. Wind protection, proper hose routing, and gas flow monitoring are essential. The authors' emphasis on gas purity is particularly important—oxygen and moisture contamination directly cause porosity.
3. Thermal management: For thick aluminum sections, the high thermal conductivity means that heat is rapidly dissipated, requiring higher energy input than expected. However, excessive heat input causes distortion and grain coarsening. The balance is achieved through preheating and interpass temperature control.
4. Electrical continuity verification: Beyond mechanical properties, the electrical resistance of the weld must be verified. Aluminum oxide formation at the weld interface can increase contact resistance, so surface preparation and proper welding parameters are critical.
5. Long-term performance: Aluminum busbars in electrolysis cells are subject to creep under sustained load at elevated temperatures. The welding process must not introduce microstructural features (such as coarse grains or precipitate-free zones) that would accelerate creep deformation.

Study Insights and Implications

This paper, while focused on a specific industrial application, provides valuable lessons for aluminum welding in general. The systematic approach to process development—starting with material selection, proceeding through parameter optimization, and concluding with comprehensive quality verification—exemplifies best practices in welding engineering. The emphasis on electrical conductivity as a performance criterion reminds us that welding applications extend beyond mechanical joining; electrical, thermal, and functional properties must all be considered.

For modern aluminum busbar applications, including those in renewable energy systems and electric vehicle battery packs, the principles established in this 1998 paper remain foundational. The key challenge has evolved from achieving adequate weld quality to achieving high productivity with consistent quality, which is where advanced process monitoring and automation come into play. Engineers should always return to the fundamentals of process understanding before embracing new technologies.