Abstract
A systematic study on the effects of solute carbon and cementite density on ductility was conducted in low-carbon Al-killed steel with 0.022 mass% C. The results obtained are as follows; 1) Total elongation was impaired by the presence of solute carbon. The deterioration is mainly caused by a decrease in local elongation; however, uniform elongation is hardly affected by solute carbon. The dynamic strain aging due to solute carbon is considered to impair local elongation, because necking is promoted by local softening when strain rate increases locally. 2) Total elongation is impaired by the presence of intragranular cementites, but is hardly affected by grain boundary cementites. Uniform elongation decreases clearly with increasing density of intragranular cementites, which is caused by a significant increase in yield strength. Furthermore, since intragranular cementites form voids, they may impair local elongation due to ductile fracture. However, when their density becomes high, in other words, they become significantly small, a slight improvement in local elongation is observed. Grain boundary cementites have no effects on the tensile properties of low-carbon Al-killed steel within the scope of the present study.
