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

Literature Overview

This paper, published in Welding (1991, No. 3), authored by Chen Baohua from Shanghai Power Plant Auxiliary Machinery Factory, presents a systematic study of high-current strip electrode overlay welding on low-carbon steel. The research compares the welding parameters, weld bead geometry, dilution rates, and overlay layer properties of high-efficiency strip electrode welding against conventional strip electrode welding. The central finding is that the overlay layer properties of both processes are comparable, while the high-efficiency process achieves approximately double the deposition rate, representing a significant productivity improvement.

Strip Electrode Welding Technology Background

Strip electrode welding (also known as submerged arc strip welding or SAW with strip electrode) is a variant of the submerged arc welding process in which a continuous flat strip of electrode material replaces the conventional round wire electrode. This configuration provides several inherent advantages: a wider and flatter arc, higher deposition rates, improved process stability, and the ability to achieve uniform multi-pass deposition with consistent layer thickness.

The high-efficiency variant achieves its productivity advantage through increased welding current and travel speed, which must be carefully balanced to maintain adequate penetration and bead geometry without excessive spatter or poor fusion.

Parameter Optimization and Weld Bead Geometry

The paper examines the effects of welding parameters on weld bead formation and dilution rate during high-current strip electrode overlay welding. Key parameters include welding current (I), welding voltage (U), travel speed (v), strip electrode width, and flux coverage.

The relationship between these parameters and the resulting weld bead geometry follows well-established welding metallurgy principles. Increasing the current increases both the penetration depth and the deposition rate, but excessive current can lead to undercut, excessive spatter, and poor bead shape. Increasing the travel speed reduces the heat input per unit length, which decreases dilution but also reduces penetration. The optimal parameter combination must balance these competing effects to achieve adequate fusion with the base metal while maintaining a reasonable dilution rate.

The dilution rate is a critical parameter in overlay welding because it directly affects the composition and properties of the overlay layer. High dilution introduces more base metal alloying elements into the overlay, potentially degrading the desired properties of the overlay material. For low-carbon steel base materials, the dilution effect is less severe than for alloy steels because the compositional difference between the base metal and the overlay material is typically smaller.

Comparison of Overlay Layer Properties

The comparison of overlay layer properties between high-efficiency and conventional strip electrode welding is the central technical contribution of this paper. The finding that the properties are comparable is significant because it validates the use of higher welding parameters without compromising the functional performance of the overlay layer.

The properties evaluated likely include hardness, tensile strength, elongation, and possibly impact toughness. The fact that these properties are maintained at comparable levels despite the doubled deposition rate suggests that the solidification conditions in the overlay layer are not significantly affected by the higher current and travel speed combination. This is consistent with the principle that the cooling rate in the overlay layer is primarily determined by the heat input per unit length (I × U / v), and if this ratio is maintained at a similar level in both processes, the microstructure and properties will be similar.

Productivity and Economic Analysis

The doubling of deposition rate represents a substantial productivity improvement. For large-scale overlay welding applications such as those encountered in power plant auxiliary machinery manufacturing, this improvement translates directly into reduced production time, lower labor costs, and increased throughput. The economic benefit is particularly significant for components requiring multiple overlay layers, where the time savings accumulate across each pass.

However, the productivity improvement must be evaluated in the context of overall process quality. Higher welding parameters may increase the rate of consumable consumption, may require more robust flux handling systems, and may increase the energy consumption per unit of deposited metal. A comprehensive economic analysis should account for all of these factors.

Engineering Practice Implications

This research is directly applicable to manufacturing environments where large volumes of overlay welding are performed on low-carbon steel components. The validation of high-efficiency parameters provides a basis for process optimization that can be implemented with existing equipment, requiring only parameter adjustment rather than capital investment.

The approach demonstrated in this paper aligns with lean manufacturing principles by identifying and eliminating non-value-added time in the welding process. The systematic comparison of conventional and high-efficiency parameters provides a data-driven basis for process improvement decisions, rather than relying on anecdotal experience or trial-and-error optimization.

Key Technical Insights

The work demonstrates that productivity improvements in welding processes can be achieved through parameter optimization without sacrificing quality, provided that the process is systematically studied and the results are validated through mechanical property testing. The principle of maintaining comparable heat input per unit length while increasing individual parameters (current and travel speed) is a fundamental approach to welding process optimization that applies broadly across welding methods.

This paper, though focused on a specific application, contributes to the broader understanding of strip electrode welding technology and provides a template for similar productivity improvement studies in other welding processes. The methodology of comparing process variants through controlled experimentation and property evaluation is a model for evidence-based process development.