High-Speed Strip Electrode Surfacing Process and Equipment A Technical Study Note

Literature Overview

The paper by Li Chunxu, Wang Xijing, Wei Jikun, and Li Heqi, published in the Journal of Welding in 1991 (Volume 12, Issue 4, pp. 208-212), presents a comprehensive study on High-Speed Strip Electrode Surfacing (HSW). The research was conducted at Gansu University of Technology and focuses on developing a self-designed HS-1500×2 welding power source and strip electrode surfacing machine. The core objective is to achieve a significant improvement in welding speed compared to conventional strip electrode electroslag surfacing (ESW) while maintaining a low dilution rate and enhancing the hydrogen-induced blistering resistance of the surfacing layer.

Core Technical Content

The HSW process represents a hybrid approach that borrows from both arc welding and electroslag welding principles. Unlike traditional electroslag surfacing, which relies on the thermal energy generated by the resistance of the slag pool, HSW utilizes a high-current arc as the primary heat source with a strip electrode fed at high speed. This fundamentally changes the thermal profile of the surfacing process.

The key innovation lies in the HS-1500×2 welding power source. This dual-channel power supply was specifically designed to provide the high current density required for rapid strip electrode melting while maintaining stable arc characteristics. The "1500" designation indicates a maximum current capacity of 1500 amperes, which is substantially higher than typical arc welding power sources of that era. The "×2" indicates a dual-channel configuration, likely enabling independent control of the surfacing and backing or flux channels.

Process Parameters and Performance Comparison

The doubling of welding speed is a remarkable achievement. In conventional strip electrode electroslag surfacing, the welding speed is typically limited to 100-200 mm/min due to the need for sufficient slag pool formation and stability. The HSW process achieves approximately double this rate by leveraging the more concentrated and rapidly responsive arc heat source.

Technical Analysis and Interpretation

The low dilution rate in HSW is attributed to the faster welding speed and the concentrated arc heat input. In electroslag surfacing, the broader heat distribution and longer dwell time tend to increase the amount of base metal melted and mixed into the surfacing layer. By increasing the travel speed, HSW reduces the base metal contribution to the weld pool, thereby preserving the metallurgical integrity of the surfacing alloy.

The improvement in hydrogen-induced blistering resistance is particularly significant for applications in the oil and gas industry, where sour service environments containing H₂S are common. Hydrogen blistering occurs when atomic hydrogen diffuses into the steel and accumulates at internal defects or inclusions, forming bubbles that can cause catastrophic failure. The improved resistance in HSW surfacing layers is likely due to:

• Reduced dilution, which preserves the beneficial alloying elements of the surfacing material
• Faster cooling rates that refine the microstructure and reduce the size of potential hydrogen trapping sites
• The arc-based process producing a cleaner, more homogeneous surfacing layer with fewer inclusions

Engineering Practice Considerations

From a practical standpoint, the HSW process offers several advantages for large-scale surfacing applications such as:

• Large diameter pipe internal surfacing for corrosion and erosion resistance
• Heavy plate repair and overlay for mining and cement equipment
• Nuclear-grade component repair requiring precise dilution control

However, the process also presents challenges. The high current requirements necessitate robust power supply infrastructure. The high welding speed demands precise strip electrode feed control and gas shielding management. Furthermore, the equipment complexity and cost of the custom HS-1500×2 power source may limit widespread adoption, particularly in smaller fabrication shops.

Study Insights and Reflections

This 1991 paper represents an important milestone in the evolution of surfacing technology in China. At a time when electroslag welding dominated heavy surfacing applications, the HSW concept demonstrated that hybrid approaches could overcome inherent limitations of single-process methods. The emphasis on hydrogen blistering resistance foreshadowed the growing demand for sour service resistant materials in the petrochemical industry.

The concept of combining high-speed arc welding with strip electrode feeding has influenced subsequent developments in robotic surfacing systems and automated overlay welding. Modern implementations of similar principles can be seen in high-deposition-rate GMAW surfacing processes and multi-wire arc surfacing systems used in modern shipbuilding and offshore construction.

The research methodology exemplifies the PDCA cycle in process development. The team identified a problem (slow ESW speed and insufficient hydrogen resistance), designed a solution (custom power source and equipment), implemented it through prototype fabrication, and verified performance through comparative testing. This systematic approach to process innovation remains a gold standard in welding technology development.

In conclusion, the HSW research by Li Chunxu and colleagues represents a pioneering effort that bridged the gap between arc welding precision and electroslag welding deposition rates. The process achieved a doubling of welding speed while maintaining low dilution and enhancing hydrogen blistering resistance, demonstrating that process innovation can simultaneously improve productivity and material performance. The custom HS-1500×2 power source and strip electrode surfacing machine developed in this study laid important groundwork for subsequent advances in high-productivity surfacing technology that continue to influence modern welding practice.