High-Efficiency Strip Electrode Overlay Welding of Low-Carbon Steel

Literature Overview

This paper, published in 1991 in the journal "Welding" (No. 3, pp. 15-19), authored by Chen Baohua from Shanghai Power Plant Auxiliary Machinery Factory, presents research on high-efficiency strip electrode (tape electrode) overlay welding for low-carbon steel components. The study systematically investigates the influence of welding parameters on weld bead geometry and dilution rate, and demonstrates that high-efficiency strip electrode welding achieves comparable weld layer properties to conventional strip electrode welding at twice the deposition rate.

Core Technical Content and Process Comparison

Strip electrode welding (also known as tape electrode or strip electrode submerged arc welding) is a specialized welding process where a continuous metal strip serves as the filler metal, surrounded by flux. This process is particularly suited for large-scale overlay applications such as boiler components, pressure vessels, and structural steel surfaces requiring wear or corrosion-resistant cladding.

Welding Parameter Effects

Parameter	Effect on Bead Geometry	Effect on Dilution Rate
Welding current	Higher current → wider, flatter bead	Higher current → increased dilution
Travel speed	Higher speed → narrower, taller bead	Lower speed → increased dilution
Strip electrode thickness	Thicker strip → deeper penetration	Thicker strip → increased dilution
Flux coverage	Affects arc stability and bead shape	Indirect effect through arc length

High-Efficiency vs. Conventional Strip Electrode Welding

The key innovation in this work is the development of high-efficiency parameters that maintain weld layer properties while doubling the deposition rate. This is achieved through optimized combinations of welding current, travel speed, and strip electrode geometry that maximize metal deposition per unit time while controlling the heat input to prevent excessive dilution.

Property	Conventional Process	High-Efficiency Process
Deposition rate	Baseline (1×)	2× baseline
Weld layer hardness	Comparable	Comparable
Weld layer microstructure	Fine grain	Comparable fine grain
Dilution rate	Controlled	Controlled (within acceptable range)
Bead uniformity	Good	Good

Process Optimization and Metallurgical Considerations

The dilution rate in strip electrode welding is a critical parameter that determines the final composition and properties of the weld layer. For low-carbon steel overlay applications, the dilution rate directly affects the carbon content and alloy element concentration in the weld metal, which in turn governs hardness, wear resistance, and corrosion resistance. The high-efficiency process must maintain dilution rates within the same range as conventional processing while increasing deposition speed, which requires careful balancing of thermal input and metal transfer rates.

The microstructural evolution in strip electrode welds is influenced by the rapid cooling rates typical of submerged arc processes. The fine grain structure of the weld layer, maintained at comparable levels in both processes, indicates that the high-efficiency parameters do not compromise the metallurgical quality. This is significant because excessive grain growth in the weld layer would reduce toughness and potentially lead to cracking during subsequent mechanical working or thermal cycling.

Engineering Application and Productivity Impact

The doubling of deposition rate represents a substantial productivity improvement for large-scale overlay operations. In power plant auxiliary machinery manufacturing, where components such as turbine casings, boiler tubes, and heat exchanger shells require extensive overlay cladding, this efficiency gain translates directly into reduced manufacturing time and cost. The process is particularly valuable for applications where the overlay thickness is substantial, as the time savings compound with each additional pass.

The methodology employed in this study—systematic parameter variation with quantitative assessment of weld geometry and dilution—represents good engineering practice that can be applied to other overlay welding processes. The use of comparative evaluation between conventional and optimized processes provides a clear basis for process qualification and standardization.

Study Reflections

This work demonstrates that efficiency gains in welding processes do not necessarily require compromises in metallurgical quality. The key to achieving both objectives lies in understanding the fundamental relationships between process parameters, thermal cycles, and microstructural outcomes. For practitioners, this paper provides a methodological framework for optimizing any welding process while maintaining quality standards, and the specific results offer practical parameter guidance for low-carbon steel overlay applications.