Comparative Study of Strip Electrode Electroslag and Submerged Arc Overlay Welding for Thick-Walled Pressure Vessels

Literature Overview

This 1997 paper by Wang Jiachun and Sun Dunwu from the Harbin Welding Research Institute, published in the journal Welding, presents a comprehensive comparative study of strip electrode electroslag overlay welding (EES) and strip electrode submerged arc overlay welding (EAS) for the internal cladding of thick-walled pressure vessels with stainless steel. The authors evaluated both processes across multiple dimensions including welding process parameters, weld bead geometry, base metal dilution rate, overlay layer properties, and fusion zone characteristics. The classification TG455 places this work within the domain of welding processes and technology.

Core Technical Points

The internal cladding of thick-walled pressure vessels with corrosion-resistant stainless steel is a critical manufacturing operation in the petrochemical, nuclear, and power generation industries. The choice between electroslag and submerged arc strip electrode processes has significant implications for productivity, deposit quality, and overall cost. The authors concluded that strip electrode electroslag welding outperforms strip electrode submerged arc welding and can serve as a replacement process for internal cladding of thick-walled pressure vessels.

Comparative Analysis

Dilution Rate Analysis

The dilution rate is perhaps the most critical parameter in overlay welding for pressure vessel cladding. A lower dilution rate ensures that the deposited layer maintains its intended corrosion-resistant composition, which is essential for the functional performance of the cladding. The authors demonstrated that EES welding achieves a lower dilution rate compared to EAS, resulting in deposit compositions closer to the intended stainless steel grade. This is attributed to the fundamental difference in heat input distribution between the two processes, with electroslag welding providing more concentrated and controlled heat input.

Weld Bead Geometry and Uniformity

The bead geometry of EES deposits is characterized by consistent width and depth with minimal variation across the weld length. This uniformity is crucial for pressure vessel cladding, where consistent coverage and thickness are required to ensure uniform corrosion protection. EAS welding, while capable of producing acceptable beads, exhibits greater variability in bead geometry, which can lead to uneven cladding thickness and potential weak spots.

Engineering Practice Considerations

For pressure vessel manufacturers, the selection of overlay welding process has direct implications for production efficiency and quality assurance. The conclusion that EES can replace EAS for thick-walled vessel cladding carries significant economic and technical weight. EES welding typically requires specialized equipment and process setup, but the improved deposit quality and reduced dilution rate justify the investment for critical applications. The fusion zone characteristics, including the presence or absence of defects such as lack of fusion, cracks, and inclusions, were also evaluated and found to favor EES.

Study Insights and Implications

This comparative study provides valuable guidance for engineers and manufacturers in the selection of overlay welding processes for pressure vessel cladding. The systematic evaluation across multiple performance dimensions establishes a rigorous basis for process selection decisions. The finding that EES outperforms EAS in dilution control and deposit quality is particularly significant for applications where the integrity of the cladding composition is paramount, such as nuclear reactor pressure vessels and petrochemical reactors operating under corrosive conditions. The work underscores the importance of process-specific optimization rather than relying on general process comparisons, and demonstrates the value of comprehensive experimental evaluation in welding technology development.