Research On Wear Mechanism And Temperature Field Feature Of Cement Conveyor Chain

In the latest years, with the development of chain transmission technology, conveyor chains are used widely in all kind of fields. Especially in cement industry with bad condition, conveyor chains are used more widely. Now cement product line from foreign countries mostly import conveyor chains. Conveyor chains made in our country usually are discarded because they are not wearable and their lives are short, which bring corporations enormous economy loss. So it becomes a key technology to study wear style and temperature field feature of cement conveyor chain working on high temperature. This thesis's central research as follows: Firstly, We study bush and pin of cement conveyor chain (NE250 type and DS250 type) after wear by means of electron microscope, and study their wear style. In addition, we analyse the fretting wear of pin. Secondly, surface hardness,center hardness,carburized layer's depth,carburized layer and center structure of bush and pin infect cement conveyor chain's wearable feature. Thirdly, we measure the temperature field cement conveyor chain for the first time, and study average temperature and instantaneous temperature of bush and pin joint affect wearable feature, and get the rule. In addition, we calculate approximately the surface temperature of bush and pin, and provide others essential base data to design bush and pin joint working on high temperature. 2. Wear style of cement conveyor chain We study bush and pin of cement conveyor chain(NE250 type and DS250 type) after wear by means of electron microscope, and study their wear style. The microcosmic wear surface as follows(Figure 1).The microcosmic wear surface of cement conveyor chain show that the wear style of DS250 chain is abrasive wear, and the wear style of NE250 chain mostly is abrasive wear, accompanied with fatigue wear.In addition, we analyse the fretting wear of pin. The microcosmic wear surface shape original surface shape as follows (Figure 2). Pin and outer plate could happen fretting wear because of their vibration. With the increase of fretting wear, many flakes unite a hole, and bush and pin assort become clearance assort. Fretting wear becomes running wear or moving wear, so chain could fall apart. 2. The influence rule of cement conveyor chain's wearable feature It is demonstrated according to micro-structure analysis that cement conveyor chain's wearable feature could be improved with high surface hardness of bush and pin,reasonable matching of carburized layer's depth and center hardness under abrasive wear mechanism. Under abrasive wear mechanism, we suggest surface hardness of bush should be HR15N≥89.5 and surface hardness of pin should be HR15N≥90.0. Cement conveyor chain's pin material is 42CrMo, after nitrocarburization,quench directly and temper with 400～450℃,has well-dispersed granulated carbide superficial layer and tempered troostite core,hence demonstrates the comprehensive mechanical features of high wear-resistance, high strength and toughness, and highresistance to plastic deformation(Figure 3). 3. Temperature field analysis of cement conveyor chain We have measured the temperature field cement conveyor chain for the first time. The real time temperature curve as follows (Figure 4 , Figure 5,Table 1 and Table 2).When cement conveyor chain works, the peak value in temperature appears on bush and pin, the valley value in temperature appears in middle of the chain plate.