Nodular cast iron crankshaft has been more and more widely cast by iron mold sand coating. As cast nodular cast iron crankshaft has high performance, can save the general normalizing process, and has considerable cost advantage. Modern research data show that the structure of pearlite matrix has higher fatigue strength than that of ferrite matrix, which is one of the important service properties of crankshaft; In addition, pearlite matrix also has higher tensile strength at room temperature and higher wear resistance.
The results show that increasing the cooling rate during austenite cooling transformation can increase the pearlite content and improve the strength of crankshaft. However, the crankshaft is usually a large section casting, which is difficult to ensure sufficient cooling rate. The usual solution is to add alloying elements such as Cu and Sb, but some elements that interfere with spheroidization will be introduced, or brittleness will be caused by the formation of carbides and enrichment at the boundary of eutectic clusters.
The as cast production of nodular graphite crankshaft can be realized by controlling the addition of alloy elements, which is bound to increase the cost. Therefore, the cooling process of crankshaft is studied, hoping to achieve the stable production of as cast nodular cast iron crankshaft without or a small amount of alloy elements by controlling the unpacking time.