CLADDING TECHNOLOGY SHANXI CO., LTDApplication of MIG Welding on Aluminum Busbars in Power Transmission Infrastructure
Literature Overview
This study by Chen Song and Sun Jianguo from the Zhongyuan Oilfield Construction Group Corporation in Puyang, Henan Province, published in 1998, addresses the application of Metal Inert Gas (MIG) welding technology to aluminum busbar fabrication in electrical power transmission systems. Aluminum busbars are critical components in high-voltage switchgear, substations, and power distribution networks where lightweight, high-conductivity conductors are required. The paper represents an early Chinese engineering contribution to aluminum welding technology in the electrical infrastructure sector, reflecting the industrial needs of the petroleum and power industries in the late 1990s.
Core Technical Content
The fundamental challenge in aluminum busbar welding lies in the material's inherent properties: low melting point (660°C), high thermal conductivity, oxide layer stability (Al₂O₃ with a melting point of 2050°C), and susceptibility to hot cracking. The authors examined MIG welding parameters including wire feed speed, travel speed, shielding gas composition, and current characteristics to achieve sound, high-conductivity joints suitable for electrical applications.
Key welding parameters investigated typically fall within the following ranges:
| Parameter | Typical Range | Notes |
|---|---|---|
| Shielding gas | 100% Ar or Ar/He mixtures | Helium addition for thick sections |
| Current | 150–400 A | Depends on thickness |
| Voltage | 18–30 V | Short-circuit transfer |
| Travel speed | 200–600 mm/min | Higher for thin busbars |
| Wire diameter | 1.0–1.6 mm | Solid aluminum wire |
| Preheating | 100–150°C | For sections >10 mm |
The study emphasized that electrical conductivity of the weld joint must approach that of the base metal to avoid localized resistive heating at the joint under operating conditions. A reduction in conductivity of more than 15–20% relative to the base aluminum alloy is generally unacceptable for busbar applications, as it creates a thermal bottleneck that can lead to progressive degradation.
Engineering Practice Interpretation
From a practical standpoint, several critical observations emerge from this work that remain relevant in modern practice:
- Surface preparation is paramount: mechanical grinding to remove the Al₂O₃ layer within 4 hours of welding is essential, as re-oxidation occurs rapidly at ambient temperature.
- Gas coverage must be optimized: aluminum busbars often have complex geometries with narrow gaps, and insufficient gas coverage leads to porosity from atmospheric nitrogen absorption.
- Heat input control is critical: excessive heat causes distortion of thin busbar sections and can lead to grain coarsening that degrades mechanical properties and conductivity.
- Post-weld treatment: stress relief annealing at 300–400°C for 1–2 hours helps relieve residual stresses without significantly affecting the temper condition of the aluminum alloy.
Defect Analysis and Countermeasures
The following table summarizes common defects encountered in aluminum busbar MIG welding and their countermeasures:
| Defect Type | Root Cause | Countermeasure |
|---|---|---|
| Porosity | Inadequate gas coverage, oxide inclusion | Improved gas nozzle design, thorough cleaning, proper gas flow rate (15–20 L/min) |
| Hot cracking | High sulfur/iron content, excessive restraint | Preheating, lower travel speed, appropriate filler metal selection |
| Undercut | Excessive current, poor technique | Reduce current, adjust torch angle, use backing bar |
| Poor fusion | Insufficient heat input, high travel speed | Increase current, reduce speed, preheat joints |
| Distortion | High thermal expansion, asymmetric weld sequence | Fixturing, back-step welding, lower heat input |
Study Insights and Implications
This 1998 study represents a foundational contribution to aluminum welding technology in China's power infrastructure sector. The principles established—particularly regarding gas protection optimization, surface preparation protocols, and conductivity preservation—remain valid today. In modern practice, the evolution from conventional MIG to pulsed MIG and hot-wire TIG has provided additional tools for heat input control, but the fundamental metallurgical challenges identified in this work persist. For engineers involved in bimetal product manufacturing, the lessons from aluminum busbar welding regarding oxide layer management and gas protection design are directly transferable to clad plate welding operations where similar aluminum-containing overlay layers are deposited. The emphasis on joint conductivity as a quality criterion parallels the bond strength and corrosion resistance requirements in bimetal pressure vessel applications.