Modification of Strip Electrode Automatic Surfacing Device for Large-Scale Industrial Applications

Literature Overview

The paper by Jiang Yunchen, published in the journal "Welding" in 2006 (Vol. 2, pp. 76-77), describes a practical engineering modification of a strip electrode automatic surfacing system at Harbin Boiler Works Co., Ltd. This work addresses the challenges of applying strip electrode surfacing to large cylindrical components that require continuous rotation during the surfacing process. The modification integrates a control box with a boring machine to achieve automatic feed control, enabling high-deposition-rate surfacing on boiler components and similar industrial equipment.

Core Technical Points

The fundamental challenge addressed in this work is the adaptation of strip electrode submerged arc surfacing (SAW-SES) to rotating cylindrical workpieces. In conventional strip electrode surfacing setups, the workpiece is stationary while the torch travels linearly. However, for large-diameter cylindrical components such as boiler drums, furnace tubes, and pressure vessel shells, the geometry demands that the workpiece rotate continuously while the torch assembly remains fixed or moves axially. This requires a synchronized control system that coordinates the rotational speed of the workpiece with the strip electrode feed rate and welding parameters.

The key modification involves integrating an automatic control box that interfaces with the boring machine's drive system. This control box serves as the interface between the welding power source, the strip electrode feeder, and the workpiece rotation mechanism. The control logic ensures that as the workpiece rotates continuously, the strip electrode feed rate and torch position are maintained within specified tolerances to produce uniform overlay layers.

Process Parameters and Configuration

The modification described in the paper focuses on achieving reliable automatic control of the surfacing process during continuous rotation. The control box likely incorporates position feedback from the rotation mechanism to modulate the strip feed rate, ensuring that the deposited bead width remains consistent regardless of minor variations in rotational speed. This is critical for maintaining overlay thickness uniformity around the entire circumference of the workpiece.

Engineering Practice Integration

In boiler manufacturing, large cylindrical components such as drum shells, furnace waterwall headers, and economizer headers frequently require surfacing to provide corrosion resistance, wear protection, or transition layers before subsequent welding operations. The strip electrode surfacing method offers deposition rates that are 3 to 5 times higher than conventional wire electrode SAW, making it economically advantageous for thick overlay requirements.

The modification described here represents a practical approach to solving a common industrial problem: adapting a linear surfacing setup to cylindrical geometry without requiring a dedicated CNC-controlled surfacing machine. By leveraging the existing boring machine as the rotational drive and adding a control box for synchronization, the plant achieves significant cost savings compared to purchasing purpose-built equipment.

The critical engineering consideration is the control of dilution rate. Strip electrode surfacing inherently produces lower dilution rates (typically 20-40%) compared to wire electrode SAW (40-70%), which is advantageous when the overlay composition must be maintained close to the nominal strip composition. However, during continuous rotation, the heat input distribution around the circumference must be carefully managed to avoid excessive dilution at the start and end points of each pass.

Key Questions and Reflections

The paper raises several important questions for practitioners. First, how does the control box handle the transition zones where the torch enters and exits the surfacing area? These regions are prone to dilution spikes and porosity formation due to the transient nature of the arc. Second, what tolerance is achievable in overlay thickness uniformity when using a modified setup rather than a purpose-built system? Third, how does the modification affect the ability to perform multi-pass surfacing with proper interpass temperature control?

From a metallurgical perspective, the continuous rotation introduces a periodic thermal cycle that may affect the microstructure of the overlay. Each point on the workpiece surface experiences a heating-cooling cycle as the torch passes, and if multiple circumferential passes are required, the thermal history becomes complex. This periodic heating can influence grain growth, phase transformations, and residual stress development in the overlay.

Study Insights and Implications

This paper demonstrates the practical engineering philosophy of adapting existing equipment through intelligent modification rather than procuring new capital equipment. The approach is particularly relevant for Chinese manufacturing enterprises that operate with constrained capital budgets but require high-quality surfacing operations. The integration of a control box with the boring machine drive system represents a simple yet effective solution to the synchronization problem.

For engineers evaluating strip electrode surfacing for cylindrical components, this paper provides a starting point for process development. The key takeaways are: (1) synchronization between rotation and feed is achievable with relatively simple control electronics; (2) the modified setup can produce acceptable results for non-critical applications; and (3) rigorous process qualification is still required to validate dilution rates, overlay composition, and mechanical properties. The paper serves as a reminder that practical engineering solutions often emerge from the creative adaptation of available resources rather than from the acquisition of the latest technology.