Zhuojin Pipe Fitting Co., LtdStrip Electrode Submerged Arc Overlay for Stainless Steel Deposits
Literature Overview and Process Background
The paper by Yu Hao, Ma Ming, and Li Wenyu from Harbin Boiler Works, published in Welding in 2012, addresses the practical application of strip electrode submerged arc welding (SAW) for depositing stainless steel overlays. Strip electrode SAW is a high-productivity process particularly suited for building up thick, uniform overlay layers on large components such as boiler tubes, pressure vessel shells, and pipe fittings. The study systematically investigated three strip electrode widths—30 mm × 0.5 mm, 60 mm × 0.5 mm, and 90 mm × 0.5 mm—to determine their respective process windows and the influence of welding parameters on deposit quality.
This work is directly relevant to engineers who need to apply corrosion-resistant or wear-resistant stainless steel overlays to thick-walled components where single-pass GTAW or FCAW would be impractical in terms of productivity and cost.
Systematic Parameter Optimization
The research methodology followed a disciplined approach of gradually adjusting welding parameters to transition from defective to defect-free deposits. The key process variables investigated included welding current, travel speed, arc voltage, electrode spacing, and stick-out length. Through iterative testing, the authors identified optimal parameter combinations that produced deposits with uniform thickness, smooth surfaces, and absence of common SAW defects such as undercut, excessive reinforcement, and lack of fusion.
| Strip Width | Typical Current Range | Travel Speed | Achieved Deposit Thickness | Key Challenge |
|---|---|---|---|---|
| 30 mm × 0.5 mm | 350–450 A | 250–350 mm/min | 4.5–5.5 mm | Narrow bead, more passes required |
| 60 mm × 0.5 mm | 500–650 A | 200–300 mm/min | 5.5–6.5 mm | Optimal balance of productivity and quality |
| 90 mm × 0.5 mm | 650–800 A | 180–280 mm/min | 5.0–6.0 mm | Wider bead, harder to control uniformity |
The final optimized parameters achieved a consistent deposit thickness in the range of 6.0 to 6.5 mm, which is a substantial single-pass buildup that significantly reduces the number of required passes compared to conventional wire electrode SAW.
Weld Metal Quality Verification
The deposited overlay layers were characterized through mechanical property testing, chemical composition analysis, and ferrite content determination. These three verification methods collectively ensure that the overlay meets both structural and corrosion resistance requirements.
- Mechanical properties: Tensile strength and hardness measurements confirmed that the deposited metal met the expected values for the selected stainless steel grade, ensuring the overlay would withstand service loading without premature failure.
- Chemical composition: Spectrographic analysis verified that key alloying elements (Cr, Ni, Mo) were within specification limits, which is critical for achieving the target corrosion resistance in the as-deposited condition.
- Ferrite content: Ferrite measurement using a ferritoscope was essential because excessive ferrite content in austenitic stainless steel overlays can promote sensitization and intergranular corrosion. The results confirmed that ferrite levels were maintained within acceptable limits (typically below 15% F.E. for general applications).
Engineering Practice Integration
From my experience with overlay applications on boiler tubes and pressure vessel components, the strip electrode SAW process offers a compelling combination of productivity and quality when parameters are properly controlled. However, the study highlights several practical challenges that must be addressed in the field.
First, strip electrode handling and feeding requires specialized equipment. The electrode must be fed from a reel through a guide mechanism, and any inconsistency in feed rate directly translates to variations in deposit thickness and composition. Operators must be trained to monitor the electrode feed system continuously.
Second, the wider bead geometry of the 60 mm and 90 mm strips demands greater precision in torch alignment and travel speed control. A slight deviation in travel speed can produce a localized area of excessive or insufficient buildup, which may require grinding and re-deposition.
Third, interpass cleaning between layers is critical. Unlike single-layer applications, multi-layer overlays require each subsequent layer to be deposited on a clean, oxide-free surface. Failure to clean thoroughly results in inclusion formation, which—as demonstrated in related research—can compromise the corrosion resistance of the final overlay.
Study Insights and Process Recommendations
The most significant insight from this work is the demonstration that strip electrode SAW can produce high-quality stainless steel overlays with deposit thicknesses of 6.0 to 6.5 mm per pass, which represents a substantial productivity gain over conventional wire electrode processes. For large-scale applications such as boiler tube bundle overlays or pressure vessel head buildup, this productivity advantage translates directly into reduced labor costs and shorter project schedules.
Engineers should note that the 60 mm strip width appears to offer the best compromise between productivity and quality control. The 30 mm strip requires more passes and is less efficient, while the 90 mm strip introduces additional challenges in maintaining uniform bead geometry. The choice of strip width should be guided by the specific geometry of the component being overlaid and the required deposit thickness.
In conclusion, this paper provides a well-documented, experimentally validated process guide for strip electrode SAW overlay of stainless steel, and the parameter ranges and quality verification protocols it presents are directly applicable to industrial overlay projects involving boiler components, pressure vessels, and heavy-duty pipe fittings.