On the hot embrittlement of continuously-cast and transfer-bar structures in DP600 advanced high-strength steel

This study reports on ultra-high temperature tensile tests (1300-1480 degrees C) performed on dual-phase (DP) advanced high-strength steels utilizing a Gleeble 3500 thermo-mechanical simulator. The thermomechanical results of both as-cast (AC) and transfer-bar (TB) material is presented, as well as three different sample geometries, to better comprehend the effect of temperature distribution and stress localization on the reproducibility of data. The results show that presence of pre-existing porosity in the AC structure decreases the ultra-high temperature strength of the material because of voids nucleation, growth and coalescence, while tearing apart of the melt in highly susceptible zones plays an important role to drastically increase the ultra-high temperature embrittlement of the TB material. It is shown that a sample with long-gauge-length (LGL) geometry provides the most consistent reproducibility as compared with other geometries; this is attributed to a combination between gentle stress localization and intensified temperature distribution along the gauge length.