Effect of chemical composition on as cast microstructure of nodular cast iron
(1) The present situation of nodular cast iron crankshaft materials is introduced, and the development trend of nodular cast iron crankshaft in three states is compared. The application of as cast nodular cast iron crankshaft in low-power engine has a long-term development prospect;
(2) The effect of microstructure on the mechanical properties of nodular cast iron crankshaft was analyzed. To improve the mechanical properties of nodular iron castings, we should not only improve the spheroidizing effect, but also ensure the state of matrix structure around the graphite ball‘‘ The pursuit of high pearlescent volume may reduce the fatigue strength to a certain extent;
(3) The cooling curves of nodular cast iron crankshaft at different unpacking times were analyzed. For iron mold sand coated casting, the cooling rate after unpacking is greater than that in the box. When the unpacking time is controlled within 10-15min, the nodular cast iron crankshaft is in austenitic state. After unpacking, eutectoid transformation is carried out at a large cooling rate, and the cooling rate reaches 33.6 ~ 55.2. C / min, higher pearlescent volume can be obtained and the strength of nodular cast iron crankshaft can be improved.