Rock Products

MAR 2013

Rock Products is the aggregates industry's leading source for market analysis and technology solutions, delivering critical content focusing on aggregates-processing equipment; operational efficiencies; management best practices; comprehensive market

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MAINTENANCE WEAR PARTS Considering Composites CHALLENGE Managing the cost of impact crusher wear parts. SOLUTION Innovative composite technology that can yield a longer lasting wear part. TIP The combination of two durable constituents results in a composite, which is longer lasting than either of the composite constituents individually. Figure 1, Wear Factor Chart If the last several years have taught us any��� thing, it is that we must be able to operate lean, especially in these trying economic times. In addition to closely managing labor and inventory, it is equally important to carefully manage consumable purchases. It is not enough to look for the lowest piece price, instead our focus needs to be on the total cost of operations. For instance, part A may have a lower unit price, however part B and its superior wear life may afford the op��� erator lower cost per operating hour and increased equipment up time. This consideration is of particular impor��� tance to operators of both vertical and hori��� zontal shaft impact crushers where a significant portion of the operating cost is the maintenance and acquisition of wear parts. Iron/ceramic composites last longer and can help reduce the number of part change outs which afford the operator with lower consumable costs, fewer mainte��� nance hours for change outs and more pro��� ductive operating hours. The most common solution to impact crusher wear parts is high���chrome iron (CrMo WI), as it offers resistance to medium impact and sliding abrasion wear (Figure 1 wear factor chart). In this chart, high���chrome white iron is shown to have a significantly better wear factor than many abrasion resistant (AR) steels, manganese steels and to some extent, chrome carbide overlays. However when crushing hard rock, even wear���resistant high���chrome iron will eventually wear out. It is possible to increase the wear resist��� ance of high���chrome iron by using compos��� ite technology where one material is added to another to yield improved combined properties. However, the manufacturing of high���chrome iron/ceramic composites in production quantities is challenging. Spokane Industries has successfully created and manufactures Si���Tec, the integration of hard ceramic material into a metal matrix, yielding a wide range of long���life wear products. To preserve this strategic posi��� tion, this successful implementer possesses several patents. High���chrome iron has been used for impact crusher wear parts for decades. Impact crushers are capable of crushing a wide va��� riety of rock ranging in hardness from lime��� stone to granite. Crushing limestone with high���chrome iron wear parts will result in low���level wear, as the feed material is much softer on a relative basis than the iron. However when crushing materials contain��� ing quartz or silicates, even high���chrome iron will tend to wear from the gouging and frequent impact of these extremely hard materials. At the other end of the extreme, using only hard ceramic material in an im��� pact crusher application would likely result in fractured ceramic material; however when the ceramic is encapsulated in a tougher material such as high chrome iron, the resulting composite is able to withstand medium impact and high abrasion. Exam��� ples of successful Si���Tec applications are shoes and feed discs, and vertical shaft im��� pact crushers, respectively. Why Composites? To understand why composites wear longer it is important to first understand why wear occurs. Wear most often occurs when the feed material is harder than the wear part material. In this case, the composite contains a constituent of high���chrome iron with very hard carbides (697 HV) as well as a ceramic constituent with a hardness of 1,900 HV. 60 ROCKproducts ��� MARCH 2013

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