Study on toughening mechanism of Ti on weld metal of high strength steel

Abstract

The effect of Ti element on acicular ferrite microstructure of high strength steel weld was studied by scanning electron microscope(SEM), Transmission electron microscopy(TEM) and EDX spectrum analysis. The results show that Ti element content in a certain range can promote the precipitation of acicular ferrite in high strength steel weld metal. The increase of Ti content in the weld makes the Ti-rich inclusions increase, which is conducive to the formation of acicular ferrite. Charpy impact test results show that with the increase of Ti content, the impact toughness of weld metal increases first and then decreases. The tensile test results show that the tensile strength of weld metal increases and the elongation decreases with the increase of Ti content. There are high density dislocations and M-A components in acicular ferrite. M-A elements hinder the crack growth and improve the impact toughness of weld metal. When the Ti content is 0.253%, the impact energy of the weld metal is 155 J at-60 °C, and the impact toughness is the best.