Overlay Welding of Hot Rolling Work Rolls Using FeCrWNiMnSi System Consumable

Literature Overview

Published in the journal Welding (2000, Vol. 12, pp. 23-25), this paper by Pan Yongming and colleagues from the Harbin Welding Research Institute documents the successful application of an FeCrWNiMnSi-based overlay welding material for the repair and refurbishment of hot rolling work rolls. The study represents an early industrial application of overlay welding technology in the metallurgical industry, specifically for hot strip and wide-spread rolling mills.

Hot rolling work rolls are critical components in steel production facilities. They operate under extreme conditions: high temperatures (up to 1200°C during rolling), intense mechanical loading, thermal cycling, and contact with hot scale. These conditions lead to rapid wear, thermal cracking, and surface degradation, necessitating frequent replacement or repair.

Technical Approach and Material Selection

The FeCrWNiMnSi system overlay material was developed by the Harbin Welding Research Institute specifically for hot rolling work roll applications. The alloy composition is designed to provide:

• High-temperature hardness: W and Cr form stable carbides that retain hardness at elevated temperatures.
• Thermal shock resistance: Ni and Mn promote austenitic phases that provide good thermal fatigue resistance.
• Oxidation resistance: Cr forms a protective oxide scale at high temperatures.
• Wear resistance: The combination of carbides and austenite provides resistance to both abrasive and adhesive wear.

The overlay welding process was applied to existing work rolls that had been worn beyond specification. Rather than replacing the entire roll, the worn surface was removed by machining, and a new overlay layer was deposited to restore the roll to service dimensions.

Process Parameters and Quality Control

The overlay welding of hot rolling work rolls presents several technical challenges:

1. Thermal distortion: The large diameter and mass of work rolls create significant thermal gradients during welding. Multi-pass welding with controlled heat input and proper travel sequencing are essential to minimize distortion.
2. Dilution control: The base metal of the work roll (typically a high-chromium or high-alloy steel) must be carefully managed to prevent excessive dilution of the overlay composition.
3. Surface preparation: The worn surface must be thoroughly cleaned and prepared to ensure good metallurgical bonding. Scale, rust, and surface contamination must be completely removed.
4. Cooling rate management: The large thermal mass of the work roll provides natural preheating, but controlled cooling is necessary to avoid cracking in the overlay layer.

The quality of the overlay repair is verified through:

• Visual inspection for surface defects (cracks, porosity, undercut).
• Hardness testing at multiple locations to confirm uniformity.
• Dimensional inspection to verify that the roll meets specification tolerances.
• Service performance monitoring to track wear rate and compare with new roll performance.

Economic and Operational Impact

The paper emphasizes the significant economic benefits of overlay welding technology for hot rolling work rolls. In the metallurgical industry, where work rolls are consumed in large quantities and at high cost, the ability to repair and refurbish rolls through overlay welding represents a substantial cost saving.

The economic advantages include:

• Reduced material cost: Overlay repair costs are typically 30-50% of the cost of a new roll.
• Reduced downtime: On-site or nearby repair facilities eliminate the need to wait for new roll delivery.
• Extended service life: The overlay material may provide equal or better wear resistance than the original roll material.
• Environmental benefit: Reduced consumption of raw materials and energy associated with new roll manufacturing.

Engineering Practice Considerations

For engineers implementing overlay welding for hot rolling work rolls, the following considerations are critical:

1. Welding consumable selection: The FeCrWNiMnSi system material must be matched to the specific service conditions of the rolling mill. Different rolling applications (hot band, hot strip, wide-spread) may require different overlay compositions.
2. Welding procedure qualification: A formal welding procedure qualification (WPQ) should be conducted to establish the optimal process parameters for the specific application. This includes wire feed speed, travel speed, voltage, gas flow rate, and interpass temperature.
3. Operator training: Overlay welding of work rolls requires skilled operators who can maintain consistent bead quality over large curved surfaces.
4. Post-weld inspection: A comprehensive inspection protocol should be established to verify the quality of the overlay repair before the roll is returned to service.

Study Insights and Reflections

This paper represents an important milestone in the industrial application of overlay welding technology. The successful deployment of the FeCrWNiMnSi system material for hot rolling work rolls demonstrated that overlay welding could be a viable alternative to complete roll replacement in high-temperature, high-wear applications.

The approach documented in this study—developing a specialized overlay consumable, qualifying the welding procedure, and implementing a systematic repair process—establishes a template that has been widely adopted in the metallurgical industry. Today, overlay welding is a standard practice for work roll refurbishment in steel mills worldwide.

A key insight from this study is the importance of matching the overlay material composition to the specific service conditions. The FeCrWNiMnSi system was not a generic wear-resistant alloy but was specifically designed for the thermal and mechanical demands of hot rolling work rolls. This principle of application-specific material design remains fundamental to overlay welding practice.

The economic case presented in this paper is compelling: overlay repair can reduce roll costs by 50-70% while maintaining or improving service performance. In an industry where work roll consumption is a significant operating cost, this represents a substantial improvement in profitability.

This study also highlights the role of research institutions in driving industrial innovation. The collaboration between the Harbin Welding Research Institute and steel companies (Anshan Steel, Harbin Environmental Protection Hydrogen Equipment Company) demonstrates the value of industry-academia partnerships in developing and implementing new welding technologies.