Effect of microalloying element crystallization on properties of ABS EH40 high strength steel plate

The ABS EH40 high strength steel plate has good low brittle transition temperature and low temperature impact toughness. In order to ensure the impact toughness of 40DEG C, reducing carbon content is a good method.

However, this will reduce the strength of ABS EH40 high strength steel plate to a certain extent, and the subsequent normalization will inevitably lead to further decrease in strength. Therefore, we need to add some microcrystalline alloy elements, such as Nb and Ti. Nb and Ti elements can expand the temperature range of deformed austenite non recrystallization zone.

Increasing the rolling amount of deformation in the non recrystallization zone of austenite is conducive to the process of hot rolling. The small dispersion produced by the pinning of nitride, carbide and carbide-nitride composite grain boundaries prevents the austenite grain from growing up and makes the grain refined and dispersed. At the same time, the precipitated particles also play an important role in enhancing precipitation.

The strength loss is compensated by fine grain strengthening and precipitation strengthening.
In addition, the ductility of ABS EH40 high strength steel plate can be improved by adding microalloying elements combined with controlled rolling and controlled cooling process.

The harmful elements such as S, P, H, O and inclusions in ABS EH40 steel have obvious effects on the toughness and ductile-brittle transition temperature. N element is the fundamental factor leading to strain aging effect. ABS EH40 high strength steel plate has higher requirements for the purity of steel. Therefore, the composition design principle of ABS EH40 normalizing plate is low C, high Mn, Nb and Ti microalloying.