Applications for hard facing in the mining industry

"Shovel buckets, scraper blades, dipper teeth, mine car wheels and hammermills are examples of equipment which require routine maintenance due to abrasion. Service life can be extended by the use 0/hard/acing and buildup materials. Mining and milling applications are described and field welding procedures discussed.A high-stress abrasion test used to select hard/acing and buildup materials/or hammers in a hammermill is described in detail. Field tests of the selected alloys confirmed their performance, and maintenance records showed a significant saving in down time and cost.The relationship between the abrasion resistance of the alloys and their hardness, work hardening, composition and microstructure is summarized. IntroductionLarge volumes of ore are handled daily by the mining industry. The abrasive nature of most ores results in extensive wear to both handling and processing equipment. If such wear is neglected it may cause lost production time and also, in extreme cases, require the complete replacement of expensive equipment. The well-planned maintenance of components subject to abrasive wear by means of buildup materials and hard facing can result in substantial economic benefits. Such benefits can , however, only be realized through the correct choice of welding process, consumables and deposition methods available to maintenance personnel. Hardfacing MethodsHardfacing is applied by a variety of methods; the three most widely used being arc welding, oxyfuel gas and thermal spraying. Table 1 summarizes the major processes used within each method. Filler metals in the form of rod, wire or powder are necessary to fulfill the individual requirements of each process. The filler rods are available in the cast form or, in the case of ductile metals or alloys, as wrought rod or tube. All types are supplied bare or flux covered. Wire is supplied in two forms, drawn flux cored and drawn solid. Powder filler metals are available in many metals or alloys; they may be simple mechanical mixtures or prefused and atomized alloys made to a specific size range and shape for optimum results for each applicable process."