Zhuojin Pipe Fitting Co., LtdSurfacing Repair of Slab Continuous Casting Machine Transfer Rolls
Literature Overview
This paper by Shan Lianying from Anyang Iron and Steel (Group) Company Sanbo Company, published in 1998 in the journal "China Metallurgy" (Vol. 8, No. 3, pp. 37-38), addresses the practical engineering challenge of repairing transfer rolls (rollway rolls) in slab continuous casting machines through surfacing techniques. The study presents a systematic approach to analyzing roll material selection, failure mechanisms, and surfacing repair methods to reduce roll consumption, lower costs, and address spare part supply shortages while improving product quality and production capacity.
Core Technical Findings
The research identifies transfer rolls as critical components in continuous casting production with high consumption rates and significant impact on production quality and capacity. Through systematic analysis of roll materials and failure causes, the author developed a surfacing repair methodology that effectively extends roll service life and reduces operational costs. This represents a practical, field-proven approach to addressing a common industrial maintenance challenge.
Roll Failure Analysis
Transfer rolls in slab continuous casting machines are subjected to severe operating conditions including:
- High-temperature contact with hot slabs (typically 800-1200°C)
- Mechanical loading from slab weight and transfer forces
- Abrasive wear from scale and oxide layers on slab surfaces
- Thermal cycling from repeated hot slab contact and cooling
- Impact loading during slab transfer operations
| Failure Mode | Mechanism | Typical Location |
|---|---|---|
| Surface wear | Abrasive contact with slab scale | Roll surface |
| Thermal cracking | Thermal cycling fatigue | Surface and subsurface |
| Spalling | Thermal stress + mechanical loading | Surface |
| Bending | Excessive mechanical loading | Roll body |
| Corrosion | Oxidation at elevated temperatures | Surface |
Surfacing Repair Methodology
The surfacing repair approach involves the following key steps:
- Removal of worn and damaged surface layers through grinding or machining
- Surface preparation through cleaning and degreasing
- Application of wear-resistant surfacing material using appropriate welding process
- Post-weld machining to restore dimensional accuracy and surface finish
- Quality inspection through dimensional measurement and surface hardness testing
The selection of surfacing material is critical and must provide adequate wear resistance, thermal shock resistance, and bonding strength with the roll base material. Typical surfacing materials for this application include high-carbon chromium steels, nickel-based alloys, or composite surfacing systems.
Process Analysis and Technical Considerations
The success of surfacing repair for transfer rolls depends on several critical factors:
- Base material compatibility: The surfacing material must have adequate bonding strength with the roll base material under thermal cycling conditions.
- Process parameter optimization: Welding parameters must be controlled to minimize dilution, porosity, and residual stresses.
- Post-weld treatment: Stress relief annealing may be required to reduce residual stresses and prevent cracking.
- Dimensional control: Post-weld machining must restore the roll to original dimensional specifications for proper casting machine operation.
Economic Analysis
The economic benefits of surfacing repair compared to roll replacement include:
- Reduced material costs (only surfacing consumable required vs. complete roll replacement)
- Reduced downtime (repair can be performed in-house with faster turnaround)
- Reduced spare parts inventory requirements
- Extended service life through periodic refurbishment
Key Questions and Reflections
An important consideration in surfacing repair of transfer rolls is the number of refurbishment cycles that can be economically achieved. Each surfacing repair requires removal of the previous surfacing layer, which reduces the base material thickness. There is a minimum viable base thickness below which the roll must be replaced. Engineers must establish maximum refurbishment cycle limits based on base material thickness and wear rate.
Another practical consideration is the integration of surfacing repair into the overall maintenance schedule of the continuous casting facility. The repair process must be coordinated with production schedules to minimize downtime, and spare rolls must be maintained to allow for continuous operation during repair cycles.
Study Insights and Implications
This research demonstrates the practical value of surfacing repair technology in addressing industrial maintenance challenges. The systematic approach to failure analysis, material selection, and process development provides a replicable framework for other equipment refurbishment applications. For continuous casting operations, the implementation of surfacing repair programs can significantly reduce operational costs and improve production reliability. The experience gained from this application can be transferred to other high-wear components in the steel industry, including guide rolls, support rolls, and other rolling mill equipment.