Submerged Arc Cladding Repair of Cold Rolling Backing Rolls Using Ceramic Flux

Literature Overview and Industrial Context

This 1997 publication by Liu Chaojian, Wu Jiyuan, and Liu Jian from Taiyuan Iron and Steel Company (TISCO) addresses the repair of cold rolling backing rolls through submerged arc welding (SAW) using ceramic (ceramite) flux. Published in Welding journal, this work reflects the critical role of roll condition in cold rolling operations, where surface quality of the backing roll directly affects the flatness and surface finish of the rolled product.

Technical Background and Process Selection

Cold rolling backing rolls are large-diameter cylindrical components (typically 800-1200 mm diameter, 2000-3000 mm length) made from high-carbon steel or bearing steel. These rolls experience severe contact stress from the work roll, leading to surface fatigue, spalling, and dimensional deviation. Traditional grinding to restore dimensions leads to significant material loss, while overlay welding can restore both dimensions and improve surface properties.

The selection of ceramic flux (ceramite flux) was a deliberate engineering decision. Ceramic fluxes differ from traditional mineral fluxes in several important respects:

The authors selected ceramic flux for its superior deoxidation properties, which produce cleaner weld metal with fewer inclusions — critical for roll surface quality. The low hydrogen absorption characteristic of ceramic flux also reduces the risk of hydrogen-induced cracking in high-carbon roll materials.

Process Parameters and Welding Strategy

The repair of cold rolling backing rolls required careful planning due to their large dimensions and the need for dimensional accuracy. The authors employed the following welding strategy:

Welding Parameters

Multi-Pass Overlay Design

The overlay was designed as a multi-pass build-up to achieve the required thickness while managing thermal input:

1. First pass: Establish good fusion with the base material, using slightly lower current to control heat input
2. Intermediate passes: Build thickness with standard parameters, maintaining interpass temperature
3. Final pass: Optimize for surface quality with controlled travel speed and adequate overlap

The total overlay thickness typically ranged from 3-8 mm depending on the extent of roll damage. The authors emphasized that the final surface of the overlay layer would be ground to the required dimensional accuracy, so the overlay thickness needed to exceed the final grinding allowance.

Quality Control and Performance Verification

The quality of the overlay layer was verified through multiple inspection methods:

The authors conducted comparative wear testing between repaired rolls and new rolls, demonstrating that properly executed overlay repair could achieve equivalent or superior service life to new rolls. This was attributed to the higher carbon content of the overlay layer, which provided enhanced surface hardness compared to the original roll material.

Study Insights and Practical Recommendations

This literature provides valuable guidance for the repair of large-diameter cylindrical components using SAW with ceramic flux. The authors' emphasis on flux selection is particularly instructive — the choice between ceramic and mineral flux can significantly impact weld quality, particularly for applications requiring clean, inclusion-free weld metal. The work also demonstrates that SAW remains a highly efficient process for large-scale overlay applications, with deposition rates 3-5 times higher than manual processes.

A key insight from this study is the importance of post-weld grinding in achieving the required surface finish for cold rolling applications. The overlay layer itself typically has a rough surface, and the final surface quality depends on the grinding process. The authors recommended using CBN (cubic boron nitride) grinding wheels for the final grinding pass to achieve the required surface finish without introducing thermal damage to the overlay layer.