Domestic Single-Layer Electrode Slag Surfacing with H316LF and SJ15F Consumables

Literature Overview

The paper authored by Yang Xiaoli and colleagues from Lanzhou Lanshi Heavy Equipment Co., Ltd. presents a systematic comparative study between domestically produced welding consumables (H316LF electrode paired with SJ15F flux) and imported Japanese equivalents (WELESS 316LJ electrode with WEL ESB F-6M flux) for single-layer electroslag surfacing (ESS) of thick-walled cylindrical shells. Published in China Chemical Equipment (2016, Vol. 18, No. 6), this work addresses a critical industrial need: the replacement of expensive imported consumables with domestically available alternatives for corrosion-resistant alloy lining applications in pressure vessels and heat exchangers.

Core Technical Approach

The study employs a rigorous comparative methodology. Both domestic and imported consumable sets are used to perform single-layer electroslag surfacing on thick-walled cylinders. The evaluation encompasses visual appearance inspection, weld surface and bond line examination, mechanical property testing, and chemical composition analysis. The objective is to verify whether domestic consumables can achieve equivalent performance to imported products while significantly reducing material costs.

The electroslag surfacing process itself is a specialized variant of electroslag welding adapted for depositing corrosion-resistant overlay layers on internal or external surfaces of thick-walled components. Unlike conventional multi-pass surfacing methods, single-layer ESS achieves deposition of a thick corrosion-resistant layer in a single pass, which is particularly advantageous for large-diameter pressure vessels and heat exchanger shells where multi-pass overlay would be prohibitively expensive and time-consuming.

Key Technical Parameters and Results

The study demonstrates that the domestic H316LF/SJ15F consumable system produces overlay layers with chemical compositions closely matching those of the imported WELESS 316LJ/F-6M system. Both systems yield 316L-equivalent austenitic stainless steel overlay layers with adequate resistance to chloride pitting and intergranular corrosion. The mechanical properties of both overlay layers satisfy relevant technical specifications for pressure vessel applications.

Engineering Practice Integration

From an engineering practice perspective, this study carries significant implications for pressure vessel and heat exchanger manufacturers in China. Single-layer ESS is particularly valuable for large-diameter cylindrical shells (typically exceeding 20 mm wall thickness) where the internal surface requires a corrosion-resistant lining. The traditional approach of multi-pass GTAW or SMAW surfacing on such thick sections would require extensive tacking, multiple layers, and substantial interpass temperature control, resulting in high labor costs and potential cracking risks.

The single-layer ESS approach eliminates these concerns by depositing a thick, dense, and homogeneous overlay in one continuous pass. The electroslag process provides excellent heat input control, slow cooling rates that promote full austenitization, and minimal dilution from the base metal due to the slag pool acting as a thermal and metallurgical buffer. However, the process requires specialized equipment including a consumable electrode holder, flux feeding mechanism, and precise travel speed control.

A critical practical consideration is the preheating requirement. For thick-walled carbon steel shells receiving a 316L overlay, preheating to 150–250 °C is typically recommended to prevent cold cracking in the heat-affected zone of the base metal. The single-layer ESS process, with its inherently high heat input, can actually help maintain adequate base metal temperature during deposition, reducing the risk of hydrogen-induced cracking.

Key Questions and Reflections

One question that arises from this study is the long-term corrosion performance of the domestically produced overlay layer under aggressive service conditions. While the chemical composition matches that of the imported product, subtle differences in microalloying elements, sulfur and phosphorus control, and grain structure could affect long-term durability in chloride-containing environments. It would be valuable to see accelerated corrosion testing data (such as ASTM G48 pitting tests or 6% FeCl₃ boiling solution tests) comparing the two consumable systems over extended periods.

Another consideration is the qualification and certification pathway. For pressure vessel applications governed by GB/T 150 or NB/T 47014, the welding procedure specification (WPS) must be qualified with the specific consumable being used. The successful application of domestic consumables in production, as reported by the authors, suggests that the qualification process has been completed and accepted by relevant inspection authorities. This is an important practical milestone that goes beyond laboratory testing.

Study Insights and Implications

This study represents a meaningful contribution to the localization of critical welding consumables in China's chemical equipment manufacturing sector. The successful substitution of imported electroslag surfacing consumables with domestic alternatives can yield substantial cost savings while maintaining equivalent technical performance. The systematic comparison methodology employed provides a replicable framework for evaluating other consumable substitutions in specialized welding applications.

For practitioners in the field, the key takeaway is that domestic consumable development has reached a maturity level sufficient for demanding overlay applications. The H316LF/SJ15F combination represents a reliable option for single-layer ESS on thick-walled cylindrical shells, provided that the process parameters are properly controlled and the welding procedure is adequately qualified. Engineers should, however, remain vigilant about consumable storage and handling conditions, as flux-cored electroslag processes are particularly sensitive to flux moisture content, which can introduce porosity and hydrogen-related defects if not properly managed.