Single-Layer High-Speed Electroslag Surfacing Technology for SA387Gr22CL2 Base Metal

Literature Overview

This paper by Zhou Bingfeng from Sinopec Nanjing Chemical Machinery Co., Ltd., published in China Chemical Equipment (2021, Vol. 23, No. 4), addresses a relatively unexplored area in domestic Chinese welding practice — single-layer high-speed electrode strip electroslag surfacing (ESS). The study uses SA387 Gr22 CL2 as the base material, an imported SOUDOTAPE 24.12.LNB electrode strip, and RECORD EST129 flux, conducting a series of process trials to determine optimal parameters. The author notes that this technique has received little research attention in China and has not yet been widely promoted, making the findings of particular practical value for engineers working on high-performance alloy components.

Core Technical Points

The study identifies several critical requirements for the success of single-layer high-speed ESS. First, the welding equipment must maintain exceptional stability throughout the process, as fluctuations in voltage or current directly affect the electroslag pool geometry and the resulting dilution rate. Second, the power supply capacity must be sufficient to sustain the high current densities required for rapid deposition without arc interruption or slag solidification defects. The author emphasizes that unlike conventional single-layer slow-speed ESS, the high-speed variant operates with a significantly elevated welding speed, which reduces the heat input per unit length while simultaneously deepening the penetration profile.

The dilution behavior is a central concern. The author systematically analyzed the compositional changes across different deposited thicknesses, calculating the dilution rates of carbon, chromium, nickel, and niobium. The results show that dilution rates are somewhat higher compared to conventional single-layer ESS, which is an expected consequence of the deeper penetration achieved at higher travel speeds. This means that the alloy composition of the deposited layer is more influenced by the base metal, and careful control of the electrode strip composition becomes essential to maintain the required wear resistance and corrosion resistance of the final overlay.

Process Analysis and Engineering Implications

The choice of SOUDOTAPE 24.12.LNB electrode strip paired with RECORD EST129 flux is noteworthy, as these are imported consumables designed for high-performance applications. The flux composition plays a critical role in controlling slag viscosity, which directly affects the stability of the electroslag pool and the uniformity of the deposited layer. Engineers should note that substituting domestic flux may require extensive requalification of process parameters, as slag chemistry significantly influences dilution behavior and microstructure formation.

From a metallurgical perspective, SA387 Gr22 CL2 is a Cr-Mo-V steel with a 2.25% Cr and 1% Mo composition, commonly used in high-temperature pressure vessel applications. The CL2 designation indicates a higher carbon equivalent, which increases the susceptibility to cold cracking. When applying high-speed ESS to such a base material, the rapid cooling rate associated with lower heat input can exacerbate the formation of hard, brittle microstructures in the heat-affected zone. The author's approach of systematically varying process parameters and measuring compositional profiles provides a rigorous methodology that can be adapted for other high-alloy base materials.

Key Questions and Reflections

The paper raises several important questions for practitioners. How does the increased dilution rate affect the long-term corrosion resistance of the deposited layer, particularly in aggressive chemical environments? The paper focuses on chemical composition but does not extensively discuss microstructural evolution, which would be critical for predicting service performance. Additionally, the requirement for high equipment stability implies that this technology is best suited for controlled manufacturing environments rather than field repair applications. Engineers considering adopting this technique should conduct thorough qualification testing, including mechanical property evaluation, microstructural characterization, and corrosion resistance testing, before committing to production use.

Study Insights and Implications

This research represents a valuable contribution to the domestic electroslag surfacing technology landscape. The findings suggest that single-layer high-speed ESS offers a compelling combination of high deposition efficiency and reduced heat input, making it attractive for large-scale overlay applications on high-alloy steels. However, the technology's dependence on stable power supply, specialized imported consumables, and careful process control means that its adoption requires significant investment in equipment and operator training. For engineers in the chemical equipment manufacturing sector, this paper provides a clear roadmap for qualification testing and process optimization, serving as a foundation for future work on extending high-speed ESS to other demanding applications.