Overlay Welding Repair of Sugar Mill Roller Journal Wear and Fatigue Cracks

Literature Overview

This paper by Pang Sixiong, Feng Chuanshan, Hu Lifang, Yang Zhongjian, and Liang Shaolu, published in Journal of Guangxi University (Natural Science Edition) (1997, Vol. 22, No. 1, pp. 91-94), documents the manual arc overlay welding repair of worn and fatigue-cracked roller journals in sugarcane sugar mill crushers. The research involved collaboration between Guangxi University's Chemical Engineering Department and two sugar mills (Yongning County Pumiang Sugar Mill and Wuming County Dongjiang Sugar Mill). The repaired rollers were put into service for two crushing seasons, processing 4.7 × 10⁵ tons of sugarcane, with no abnormal failures observed and overlay wear of only 0.3 mm.

Service Conditions and Failure Modes

Sugarcane sugar mill crushers operate under severe conditions that combine multiple degradation mechanisms:

The primary failure modes of roller journals include:

1. Abrasive wear: Caused by hard particles and fibers embedded in the sugarcane.
2. Fatigue cracking: Resulting from cyclic contact stresses at the journal bearing surface.
3. Corrosion-wear synergy: The wet environment promotes corrosion, which accelerates wear.
4. Adhesive wear: Metal-to-metal contact under high pressure and sliding conditions.

Repair Methodology

The repair technique employed manual metal arc welding (SMAW) overlay welding, which is a practical and cost-effective approach for field repair of large components. The key aspects of the repair methodology include:

The repair process likely involved the following steps:

1. Inspection and assessment: Visual inspection, magnetic particle testing (MT) per GB/T 26951 or equivalent to detect surface and near-surface cracks.
2. Surface preparation: Grinding of the worn surface to remove all damaged material, creating a clean, flat surface for welding.
3. Crack treatment: For fatigue cracks, grinding of the crack to a blunt-bottom groove, followed by stress relief welding (TIG welding) to prevent crack propagation during the overlay welding process.
4. Overlay welding: Multi-pass SMAW overlay welding with appropriate electrode selection.
5. Post-weld machining: Turning or grinding to restore the journal to its original dimensions and surface finish.
6. Final inspection: Dimensional verification, surface finish measurement, and hardness testing.

Performance Validation

The service validation data is particularly valuable:

• Duration: Two complete crushing seasons (approximately 2 years of operation)
• Throughput: 4.7 × 10⁵ tons of sugarcane processed
• Overlay wear: 0.3 mm total wear over two seasons
• No abnormal failures: No cracks, spalling, or delamination observed

The wear rate of 0.3 mm over two seasons (approximately 8000-12000 operating hours) corresponds to a wear rate of approximately 0.03-0.04 mm per 1000 hours. This is an excellent result for overlay repair in such a demanding application, indicating that the overlay material and welding process provided adequate protection.

Material Selection and Process Optimization

For sugar mill roller journal repair, the following considerations are critical:

The selection of low-hydrogen electrodes is critical for preventing hydrogen-induced cold cracking, particularly in the heat-affected zone (HAZ) of the base material. The base material of sugar mill rollers is typically a medium-carbon steel (e.g., 42CrMo or 40Cr), which is susceptible to hydrogen cracking if not properly preheated.

Engineering Practice Implications

This paper demonstrates the practical viability of field repair of sugar mill roller journals using SMAW overlay welding. Several lessons can be drawn for maintenance engineering:

1. Economic justification: The cost of overlay repair is significantly lower than roller replacement, particularly for large-diameter journals. The repair extends service life by at least two seasons, providing substantial economic benefit.
2. Quality control: The absence of failures over two seasons validates the repair procedure, but regular inspection during operation is still recommended. Ultrasonic testing (UT) of the overlay-bond interface should be performed at the end of each season to detect any delamination.
3. Procedural standardization: The repair procedure should be documented as a formal procedure with defined parameters, inspection requirements, and acceptance criteria. This aligns with the principles of procedural welding per ASME BPV Code Section V or NB/T 47013.
4. Predictive maintenance: The measured wear rate of 0.3 mm per two seasons can be used to predict the remaining service life of the repaired journal, enabling proactive maintenance scheduling.

Key Reflections

The simplicity of the repair method (manual arc welding) and its successful long-term performance is noteworthy. In an era of increasingly sophisticated welding technologies, this paper reminds us that practical, proven methods often provide the best balance of cost, reliability, and serviceability. The field repair capability is particularly valuable for remote sugar mill locations where access to advanced welding equipment may be limited.

However, several aspects of the repair procedure are not detailed in the paper, which limits its direct applicability as a procedural specification. The electrode type, preheat temperature, welding parameters, and post-weld heat treatment are not explicitly specified. Engineers implementing this repair method should develop a qualified welding procedure specification (WPS) based on the principles described, with appropriate qualification testing per relevant standards.

The fatigue crack repair aspect deserves particular attention. Fatigue cracks in roller journals are a serious concern because they indicate a potential for catastrophic failure. The repair of fatigue cracks requires not only surface overlay but also careful treatment of the crack root to ensure complete fusion and stress relief. The paper's positive results suggest that the repair procedure was adequate, but a more detailed analysis of the crack repair technique would be valuable for future reference.

Study Insights

This paper provides a practical case study of overlay welding repair in the sugar processing industry, demonstrating that manual arc welding overlay repair can provide reliable, long-term service life extension for worn and cracked roller journals. The two-season validation with 4.7 × 10⁵ tons of sugarcane processed and only 0.3 mm of overlay wear represents a successful repair outcome. For maintenance engineers in the sugar industry and related heavy-duty processing applications, this paper offers a proven repair approach that balances technical effectiveness with economic practicality. The key to success lies in proper surface preparation, appropriate electrode selection, controlled welding parameters, and thorough post-weld machining and inspection. This case reinforces the fundamental principle that sound welding practice, even with simple equipment, can deliver reliable results when applied with proper technique and quality control.