Zhuojin Pipe Fitting Co., LtdDevelopment of Wear-Resistant Surfacing Electrodes for Hot Rolling Rolls
Literature Overview
This paper, published in the Chinese Journal of Welding in 1997 by Ying Pengzhan, Ge Changlu, and Cai Yingjun from China University of Mining and Technology in Xuzhou, reports on the development of a wear-resistant surfacing electrode specifically designed for hot rolling rolls. Funded by the Ministry of Coal Industry, this research addresses a significant industrial challenge: the premature wear of hot rolling roll surfaces under severe abrasive and adhesive wear conditions. The authors systematically investigated the electrode flux composition, identified an optimal alloy system, and validated the resulting surfacing deposit through metallographic analysis, X-ray diffraction, hardness testing, and both laboratory and industrial wear trials. The results demonstrate a substantial improvement in wear resistance compared to conventional 45 steel, making this work highly relevant to the steel rolling industry.
Alloy Design and Microstructural Characterization
The development of a wear-resistant surfacing electrode for hot rolling rolls requires balancing several competing requirements: sufficient hardness to resist abrasive wear, adequate toughness to withstand impact loading from the rolled stock, resistance to thermal fatigue under the elevated operating temperatures, and good weldability with the roll base metal. The authors adopted a systematic approach of iteratively adjusting the flux composition to identify the optimal alloy system.
The resulting surfacing alloy exhibits a microstructure consisting of martensite, retained austenite, and carbides. This combination is characteristic of high-carbon, high-chromium alloy steels and is well-suited for wear-resistant applications. The martensite provides the primary hardness contribution, the retained austenite offers transformation toughening under impact loading, and the carbides serve as hard second-phase particles that resist abrasive penetration.
| Characterization Method | Key Findings |
|---|---|
| Optical microscopy | Martensite matrix with dispersed carbide particles; retained austenite in intergranular regions |
| X-ray diffraction | Confirmed phases: martensite (BCC), retained austenite (FCC), and carbide phases |
| Hardness measurement | HRC 58–60 across the surfacing layer |
| Wear testing (abrasive) | Wear resistance 6.1 times that of 45 steel |
| Aging test (580°C, 1000 min) | Hardness retained at HRC 58–59 after aging |
The hardness of HRC 58–60 places this alloy in the upper range of typical surfacing deposits for hot rolling rolls, which is critical for resisting the severe abrasive wear caused by the interaction between the roll surface and the hot steel strip. The presence of retained austenite is particularly beneficial because it can transform to martensite under impact loading, absorbing energy and preventing crack propagation. This transformation toughening mechanism is a key factor in the alloy's ability to withstand the cyclic loading conditions encountered during hot rolling.
Wear Mechanism Analysis
The authors conducted both high-stress abrasive wear tests and industrial trials to validate the wear resistance of the surfacing alloy. The laboratory tests simulated the abrasive conditions encountered during hot rolling, where the roll surface is subjected to continuous sliding contact with the hot steel strip under high contact pressure. The industrial trials provided real-world validation under actual production conditions.
The wear resistance of 6.1 times that of 45 steel represents a substantial improvement that translates directly into extended roll life and reduced production downtime. This improvement is attributed to the combined effect of the high hardness of the martensitic matrix, the presence of hard carbide particles that resist abrasive penetration, and the transformation toughening provided by retained austenite. The fact that the hardness is maintained at HRC 58–59 after aging at 580°C for 1000 minutes is particularly significant, as it indicates that the alloy possesses excellent thermal stability and will not soften significantly during normal hot rolling operations where the roll surface temperature can reach several hundred degrees Celsius.
Engineering Practice and Application Considerations
For engineers involved in hot rolling roll maintenance and refurbishment, this paper provides practical guidance on the selection and application of wear-resistant surfacing electrodes. Several key considerations arise from the research findings:
- The surfacing layer must be applied with appropriate preheat to avoid cracking at the interface between the surfacing deposit and the roll base metal.
- The number of surfacing passes should be optimized to ensure uniform hardness and microstructure throughout the deposit thickness.
- The surfacing electrode should be used with the recommended polarity and arc voltage to achieve optimal dilution and alloy transfer.
- Post-surfacing stress relief may be required to prevent cracking during subsequent machining or grinding operations.
- The surfacing layer thickness should be sufficient to accommodate the wear allowance during the roll's service life.
The industrial trial results provide confidence that the surfacing alloy can withstand the severe conditions of hot rolling production. However, engineers should be aware that the actual wear life in service may vary depending on the specific rolling conditions, including the steel grade being rolled, the rolling temperature, the rolling speed, and the lubrication conditions.
Study Insights and Reflections
This paper exemplifies the systematic approach to surfacing alloy development that is essential for solving real-world engineering problems. The iterative optimization of the flux composition, combined with rigorous metallurgical characterization and practical wear testing, provides a model for similar research endeavors. The emphasis on thermal stability, as demonstrated by the aging test at 580°C, reflects a practical understanding of the service conditions that the surfacing deposit must endure. For engineers in the steel rolling industry, this work demonstrates that targeted surfacing alloy development can yield substantial improvements in roll life and production efficiency, justifying the investment in research and development. The findings also highlight the importance of understanding the wear mechanisms involved, as this knowledge enables the rational design of surfacing alloys tailored to specific service conditions rather than relying on empirical trial and error.