(1) In laboratory experiments, applying ultrasound during solidification can refine the microstructure of nodular cast iron, increase the roundness of nodular cast iron and reduce the content of ferrite. The mechanical properties of ultrasonic treated specimens are slightly better than those without ultrasonic treatment.
(2) In the laboratory experiment, ultrasonic treatment was applied to one of the cavities after the spheroidization of nodular cast iron. The average number of graphite balls is 93 when ultrasonic treatment is applied twice, and 41 when ultrasonic treatment is applied only once in the spheroidization process of nodular cast iron; The ferrite content of the former is 7.24%, which is less than 10.60% of the latter. The elongation of the former is 7.3% and the latter is 6.6%. There is little difference in tensile strength, impact toughness and hardness between the two. It shows that applying twice ultrasound can refine the microstructure of nodular cast iron, increase the number of graphite balls, reduce the ferrite content, and slightly improve the mechanical properties.
(3) Under the same experimental conditions, the time of ultrasonic application in the spheroidization process of nodular cast iron was increased from 1 min to 2 min, the number of graphite balls was increased from 41 to 63, and the ferrite content was reduced from 10.60% to 2.254%. The tensile strength, impact toughness and hardness of the specimen with longer ultrasonic action time are 864mpa, 37.4mpa and 270hb, while the tensile strength, impact toughness and hardness of the specimen with shorter ultrasonic action time are 822mpa, 35.7mpa and 249hb. The tensile strength and impact toughness increased by about 5% with the increase of action time. It shows that increasing the ultrasonic application time in the spheroidizing process of nodular cast iron can refine the microstructure and improve the comprehensive mechanical properties.
(4) In the factory experiment, the method of continuous application of ultrasonic wave is adopted, the ultrasonic output power is low, and the influence on the tissue is not obvious; When ultrasonic was applied in pulse mode, the ultrasonic output power was increased from 200W to 400-500w. It was observed that the microstructure of nodular cast iron was refined, the number of graphite balls increased and the size was uniform; The elongation and impact energy are about 10% higher than the former, and the tensile strength is basically unchanged. The mechanical properties of both are higher than those of the original as cast crankshaft. The tensile strength of the crankshaft after ultrasonic treatment is 800-900mpa and that of the as cast crankshaft is about 700MPa, an increase of 14% – 28%.