External Field Treatment Refining Microstructures of Pipe-line Steel SAW Weld

The effects of electrom agnetic stirring and TIG surface treat process on the microstructu res of pipe-line steel SAW deposited metals were investigated. The results showed that electromagnetic stirring changed the size and distribution of inclusions in deposited metals,increased the density of inclusions with 0.20.6 μm diameter, promoted the formation and refining of acicular ferrite within austenite gains. The contents of AF within austenite gains were increased from 85.1% to 91.7% and the low temperature toughness of deposited metal was improved. TIG surface treat process eliminated column gain structures of surface layer of welds. The size of acicular ferrite was greatly refined and grain boundary ferrite and side-plate ferrite disappeared.