Zhuojin Pipe Fitting Co., LtdOverlay Welding of Hot Rolling Work Rolls Using FeCrWNiMnSi Alloy
Literature Overview
Pan Yongming et al. (2000, published in Welding, Vol. 2000, No. 12, pp. 23-25) report on the successful application of FeCrWNiMnSi-based overlay materials for hot rolling work roll repair and hardfacing. The research was conducted in collaboration between the Harbin Welding Research Institute, Anshan Steel Company's Equipment Department, and Harbin Environmental Protection Hydrogen Equipment Industrial Company. This study represents an important industrial application of overlay welding technology in the metallurgical industry, demonstrating significant economic benefits through extended roll service life.
Technical Background and Application Context
Hot rolling work rolls are subjected to extreme combined loading conditions:
- High temperature: Surface temperatures of 600-1000°C during rolling of hot steel
- Heavy mechanical loading: Contact stresses exceeding 2000 MPa
- Thermal cycling: Repeated heating and cooling during the rolling process
- Chemical attack: Scale spalling, oxidation, and iron diffusion from the rolled product
- Abrasive wear: From oxide scale and impurities in the steel being rolled
These combined degradation mechanisms result in roll surface damage characterized by thermal cracking, spalling, wear, and oxidation. The conventional approach of grinding rolls back to size results in significant material loss and shortened service intervals. Overlay welding provides a superior alternative by depositing a wear-resistant, heat-resistant alloy layer that can withstand the harsh rolling conditions.
Overlay Material Design
The FeCrWNiMnSi alloy system was developed by the Harbin Welding Research Institute specifically for hot rolling work roll applications. The alloy composition is designed to provide:
| Alloying Element | Function | Typical Range |
|---|---|---|
| Cr | Oxidation resistance, solid solution strengthening | 10-20% |
| W | High-temperature strength, carbide formation (WC, W₂C) | 5-10% |
| Ni | Toughness, austenite stabilization, hot workability | 3-8% |
| Mn | Hardness, carbide formation | 1-3% |
| Si | Deoxidation, solid solution strengthening | 0.5-2% |
The resulting microstructure typically consists of tempered martensite with fine carbide particles (WC, W₂C, M₇C₃) and retained austenite. This combination provides excellent hot hardness, thermal shock resistance, and wear resistance.
Process Parameters and Application Methodology
The overlay welding process for work rolls typically involves:
- Surface preparation: Grinding the roll surface to remove damaged material, followed by cleaning and preheating to 200-300°C to prevent cracking in the base metal.
- Deposition: Multiple passes of overlay material are applied using submerged arc welding (SAW) or flux-cored arc welding (FCAW) for high deposition rates. The overlay thickness typically ranges from 3-8 mm.
- Post-weld treatment: Controlled cooling or tempering to optimize hardness and relieve residual stresses.
- Machining: The overlay surface is ground to the required dimensional accuracy and surface finish for rolling service.
Economic Benefits and Industrial Impact
The study reports significant economic benefits from implementing work roll overlay welding technology in the metallurgical industry:
- Extended service life: Overlay rolls achieve 2-4 times the service life of conventionally manufactured rolls before requiring regrinding or replacement.
- Reduced downtime: Roll changes are less frequent, improving production continuity.
- Material savings: Only the damaged surface is replaced, preserving the expensive roll core material.
- Cost reduction: The total cost per ton of steel rolled is reduced by 15-30% through extended roll life.
Engineering Practice Considerations
For engineers implementing work roll overlay welding programs, several critical factors must be addressed:
- Base metal compatibility: The overlay material must have good metallurgical bonding with the roll core steel (typically 48Cr2MoV or similar high-alloy tool steel). Preheating and interpass temperature control are essential to prevent base metal cracking.
- Residual stress management: The high residual stresses from overlay welding can cause spalling during rolling service. Post-weld tempering at 550-650°C for sufficient duration is recommended.
- Thermal shock resistance: The overlay must withstand repeated thermal cycling without cracking. The Ni content in the alloy is critical for maintaining toughness at elevated temperatures.
- Process control: Consistent welding parameters and interpass cleaning are essential to prevent porosity, lack of fusion, and inclusion defects that would compromise service life.
Study Insights
This study demonstrates the maturity of overlay welding technology for critical industrial applications. The successful industrial implementation at Anshan Steel Company validates the technical approach and provides a model for other steel mills considering similar technology adoption. The key lesson for engineers is that overlay welding is not merely a repair technique but a design strategy that can fundamentally improve the cost-effectiveness and reliability of critical rotating equipment in metallurgical processing.