Study On The Relationship Between Organization And Performance Of Crankshaft Material

As one of the main parts of internal combustion engine, the main role of crankshaft is to transform reciprocating motion into rotation movement of the engine piston and connecting rod. Its quality directly determines the engine’s performance and life. In the working process of engine, crankshaft has to withstand heavy load and ever-changing bending moment and torsion, which can causes the accidents and defects of crankshaft fracture. With the increasing demand of high-power engine, the crankshaft with higher strength and better wear resistance is needed to meet the higher requirements.The failure analysis of crankshaft has been made in the paper by the metallographic test, scanning electron microscopy (SEM) and wet chemical analysis (WCA). The trace elements in the ductile cast iron are also analyzed. The conclusions are made as follows1) The fracture behavior of crankshaft installed in the heavy truck happens during the travelling process. The investigation aiming at the raw materials shows that compared to the forging steel made from another plant, the crystal grain is coarse and the content of phosphorus is2times higher than that of another plant.2) The investigation on thermal fracture behavior of non-quenched and tempered steel caused during the heating process indicates that both content of carbon and oxide-are above their standard.3) The observation on the microstructure and fracture topography of QT900-5and QT900-2shows that the difference of interlamellar spacing of pearlite of the two samples is quite close, but the graphite nodule of QT900-5is fine and even, and the though fracture is observed on the sample. Comparatively, the size of graphite nodule of QT900-2is coarse and its distribution is not so even. The mixture ratio of Cu and Sn plays an important role in the development of toughness of nodule iron. The addition of a certain amount of Cu to the nodule iron can promote the formation of graphite nodule, while the addition of Sn can promote the even distribution of nodule, therefore, refine pearlite and graphite nodule.