Toughness of HSLA-100 copper treated steels

The mechanical properties of a series of HSLA-100 copper treated steels with different carbon and rare earth metals (REM) contents were evaluated. The steels used in this study were heat treated to exhibit yield strengths (YS) in the range of 670 - 860 MPa. Of particular interest in this study were the effect of C and REM contents on the CTOD fracture toughness (σm), upper shelf energy (USE) and fracture appearance transition temperature (FATT) of the steels. The results obtained clearly showed the deterioration of the impact and fracture toughness properties of the steels tested as the carbon content increased. Similar effect was observed with the total inclusion projected length per unit area (Σb). (author)