Effect of La–O–S complex inoculant on microstructure and mechanical characteristics of ductile iron

The effects of rare-earth (RE) inoculants are excellent, but RE is rare and expensive. Consequently, it is necessary to choose other elements to reduce the use of RE. In this paper, research was done to investigate the effects of different content La–O–S complex inoculant on the microstructure and mechanical characteristics of ductile iron (DI) through SEM, EDS, XRD, etc. Studies have shown that the as-cast structures of the samples are graphite nodules, ferrites, and a few pearlites. The graphite core consists of oxides (Al 2 O 3 , SiO 2 , Fe 2 O 3 ), sulfides (La 2 S 3 , LaS), and XO·SiO 2 ·Al 2 O 3 silicate (X: Ca, Ba, Sr). The amount of graphite nodules increases firstly and then slightly decreases, ferrite increases gradually, and pearlite decreases by degrees with the increase in S or O content, which makes the Brinell hardness and tensile strength of the sample decrease, and the elongation of the sample slightly decreases after increasing. When both O and S are 0.3%, mechanical characteristics of the samples are best, Brinell hardness is 163.3 BHW, tensile strength is 513 MPa, and elongation is 16.1%.