Eliminating roll arcing

Roll arcing, the roughening of mill rolls through a welding process, is a significant health, safety and environmental risk due to almost continuous exposure during the crushing season. Staff work on or near high-energy, rotating machinery, often in the presence of high-temperature vapour. This paper reports on a project that involved trials to evaluate alternative roll coatings that do not require arcing, providing performance data to determine the most cost-effective approach to eliminate roll arcing. Two rolls at Racecourse Mill were coated. Metal inert gas (MIG) welding and laser cladding approaches were trialled for coating the root and flanks of the roll grooves, with the MIG welding approach being more economical. There remains considerable potential to optimise the laser cladding process to reduce its cost. MIG welding incorporating tungsten carbide chips was used to coat the tips of the grooves. Information has also been gained to estimate the life of the coating. While the technology of cladding has advanced, there remain challenges to its widespread adoption. While it is possible to eliminate roll arcing on the top roll, further work is required for the tip cladding to consistently survive a full season. In particular, further work is required for the tip cladding to survive a second full season following a minor refurbishment. If these results can be achieved, the economics of cladding will improve substantially.