Influence of Zirconium Content on Microstructure and Toughness of X70 Steel Weld Metal

Zirconium was transferred from the flux to the weld metals through adding Fe-Zr alloy in the weld flux. The influence of zirconium on microstructure and toughness of X70 steel weld metal was studied.The results show that the addition of Zr increases the content of acicular ferrite and improves the microstructure of weld metal.The results of Charpy-V tests have displayed that the weld metal obtains the best toughness at a content of 0.006 wt.% of Zr.Above the level,although the weld metal still obtains a relative high content of acicular ferrite,due to the formation of island-like martensite-austenite(M-A),toughness of the weld metal is reduced.