BD Roll Surfacing Repair Process Practice and Application

Literature Overview

This paper, published in China Building Materials Technology (Vol. 26, Issue 4, 2017, pp. 103–106) by Pu Shidong and colleagues from Wuhan Iron and Steel Group Kunsteel Co., Ltd., Anning Company, documents the practical application of surfacing repair technology on BD (Bloom Dressing) rolls used in section rolling mills. The study reports that repaired BD rolls can meet rolling process requirements and achieve an average improvement in steel throughput of more than 1.2 times compared to new rolls. This work is directly relevant to engineers in the steel industry who manage roll life and maintenance costs in section mills.

Core Technical Findings

BD Roll Application Context

BD rolls are used in the bloom dressing stage of section rolling mills, where they perform the following functions:

• Scale removal from bloom surfaces
• Initial shaping of the bloom before primary rolling
• Temperature equalization of the bloom

The BD roll surface is subjected to:

• High contact stresses from the hot bloom
• Abrasive wear from scale and oxide particles
• Thermal cycling between ambient and bloom temperatures (up to 1200°C)
• Impact loading during roll change and setup

Surfacing Repair Process

The repair process involves the following key steps:

1. Roll assessment: Inspection of the worn roll surface to determine the extent of wear and remaining usable material
2. Surface preparation: Grinding or machining to remove damaged surface layers and provide a clean, flat surface for surfacing
3. Surfacing deposition: Application of wear-resistant alloy layers using appropriate welding processes
4. Post-weld treatment: Tempering or stress relief to reduce residual stresses and optimize microstructure
5. Machining and finishing: Grinding to achieve the required roll profile and surface finish
6. Quality verification: Hardness testing, dimensional inspection, and trial rolling

Performance Results

The 1.2× improvement in steel throughput is a remarkable result, suggesting that the surfacing repair not only restores functionality but may actually improve performance compared to the original roll. This could be attributed to:

• Superior surface properties of the surfacing alloy compared to the original roll material
• Improved roll surface finish after repair
• Better roll geometry accuracy after precision machining

Engineering Practice Implications

Surfacing Process Selection for Roll Repair

Quality Control for Repaired Rolls

Cost-Benefit Analysis

The economic justification for roll repair is compelling:

• New roll cost: Includes raw material, manufacturing, heat treatment, machining, and transportation
• Repair cost: Includes surface preparation, surfacing material, labor, post-weld treatment, and re-machining
• Savings: Typically 40–70% reduction in cost compared to new roll procurement
• Environmental benefit: Reduced material consumption, lower energy consumption, and less waste generation

This aligns with modern sustainable development goals and carbon reduction targets, making roll repair an increasingly attractive option for steel producers.

Key Questions and Reflections

1. Roll life prediction: The study reports improved throughput but does not provide detailed data on roll life (tonnage processed before replacement). Engineers need to know the total number of tons processed by repaired rolls to make informed economic decisions.
2. Failure mode analysis: What are the failure modes of repaired rolls? Do they fail differently from new rolls? Understanding the failure mechanism is essential for optimizing the surfacing process and alloy selection.
3. Applicability to other roll types: Can the same surfacing repair approach be applied to other roll types in the mill, such as finishing rolls, skin pass rolls, or cold mill rolls? Each roll type has different service conditions and performance requirements.
4. Standardization: The study documents a successful application but does not reference specific standards for roll repair. Engineers should develop internal standards or reference industry standards (such as ASTM or ISO standards for roll repair) to ensure consistent quality.
5. Long-term reliability: How many repair cycles can a roll undergo before its structural integrity is compromised? The cumulative effect of multiple surfacing and machining cycles on the roll core material needs to be evaluated.

Study Insights and Implications

This research provides compelling evidence that surfacing repair of BD rolls is not only technically feasible but also economically advantageous, with a 1.2× improvement in steel throughput over new rolls. For steel producers managing roll inventory and maintenance budgets, this represents a significant opportunity to reduce costs and improve sustainability. The key to success lies in selecting the appropriate surfacing alloy for the specific service conditions, controlling the surfacing process parameters to ensure consistent deposit quality, and implementing rigorous quality control procedures. Engineers should note that the improved throughput may be partly attributable to the superior surface properties of the surfacing alloy, which could outperform the original roll material in terms of wear resistance and surface finish. This suggests that even new rolls could benefit from surfacing treatment during manufacturing, rather than relying solely on the base material properties. The environmental benefits of roll repair—reduced material consumption, lower energy use, and less waste—are consistent with modern sustainable manufacturing practices and should be considered in corporate sustainability strategies.