Development and Characterization of Wear-Resistant Surfacing Electrodes for Hot Rolling Rolls

Literature Overview

This paper by Ying Pengzhan, Ge Changlu, and Cai Yingjun from China University of Mining and Technology (Xuzhou), published in the "Welding Journal" (1997, Vol. 18, No. 2, pp. 6-10), reports on the systematic development of a wear-resistant surfacing electrode specifically designed for hot rolling rolls. Hot rolling mills operate under extremely demanding conditions where roll surfaces are subjected to high temperatures (up to 580°C or higher), severe abrasive and adhesive wear from the moving steel strip, and repeated thermal cycling. The service life of rolls is a critical economic factor in steel mill operations, and surfacing is the primary method for restoring worn roll surfaces and extending roll life. This research was funded by the Ministry of Coal Industry, reflecting the practical industrial need that drove this work.

Alloy Design and Microstructure

The authors employed an iterative approach to developing the electrode composition, systematically adjusting the flux coating formulation to achieve the desired alloy system for hot rolling roll surfacing. The final alloy system was characterized by metallographic examination and X-ray diffraction analysis, revealing a microstructure consisting of martensite (M) + retained austenite (γ') + carbides. This triphasic microstructure is well-established in the literature as providing an optimal balance of hardness, toughness, and wear resistance for hot working applications.

Key Metallurgical Parameters

The retained austenite component in this microstructure serves a dual purpose: it contributes to the overall toughness of the surfacing layer, reducing the risk of spalling and cracking under impact loading, and it provides a transformation-induced plasticity (TRIP) effect that enhances wear resistance by work-hardening during the wear process. The carbides, likely consisting of M₇C₃ and M₆C type carbides, provide the primary abrasive wear resistance by acting as hard reinforcement phases within the martensitic matrix.

Thermal Stability Analysis

A particularly significant finding is the excellent thermal stability of the surfacing layer. After aging at 580°C for 1000 minutes, the hardness remained in the range of HRC 58-59, indicating minimal softening. This is critical for hot rolling applications where the roll surface temperature can reach 550-650°C during operation. Many conventional surfacing alloys experience significant softening at these temperatures due to carbide dissolution and martensite decomposition, leading to rapid wear. The thermal stability observed in this alloy suggests that the carbide morphology and distribution are resistant to coarsening at elevated temperatures, and that the martensite has a high carbon content that stabilizes the structure against tempering.

Wear Testing Methodology and Results

The authors employed both laboratory-scale high-stress abrasive wear testing and industrial field trials to validate the performance of the new electrode. The laboratory testing followed standardized wear test protocols, while the industrial trials provided real-world validation under actual mill conditions.

The 6.1-fold improvement in wear resistance compared to 45 steel is a substantial result. For context, 45 steel (a medium-carbon steel with approximately 0.45% C) is a common base material for hot rolling rolls before surfacing. The dramatic improvement in wear resistance translates directly into extended roll life, reduced downtime for roll changes, and lower operating costs for the steel mill.

Practical Implications for Mill Operations

Study Insights and Reflections

This paper represents a classic example of applied metallurgical research driven by industrial need. The systematic approach to alloy design—iteratively adjusting the flux composition to achieve the desired alloy system—demonstrates the practical methodology that materials engineers must employ when developing new consumables. The emphasis on both laboratory testing and industrial validation is particularly commendable, as laboratory results alone cannot fully predict field performance.

The finding that the alloy maintains its hardness after prolonged exposure at 580°C is of particular significance. In practice, hot rolling roll surfacing alloys must resist not only wear but also thermal degradation. Many commercially available surfacing electrodes achieve high initial hardness but lose it rapidly at elevated temperatures, leading to premature failure. The thermal stability demonstrated in this study suggests that the alloy design successfully addresses both the wear and thermal challenges simultaneously.

For engineers selecting surfacing consumables for hot rolling applications, this paper provides valuable guidance on the importance of matching the alloy microstructure to the specific service conditions. The martensite + retained austenite + carbide structure is not merely a high-hardness combination but a synergistic microstructure where each phase contributes to the overall wear resistance through different mechanisms.