The Effect of Weld Metal Manganese Content on the Microstructure, Mechanical Properties and Hot Crack Susceptibility of Helically Welded Linepipes

摘要: The effect of manganese addition on decreasing hot crack susceptibility submerged arc welding in microalloyed steels is well understood, but its increment should not cause unsuitable changes metallurgical and mechanical properties weld metal. Therefore, since metal Mn content SAW process mainly controlled by wire composition, the aim this investigation to study microstructure, helical linepipes In regard, three different wires with 0.88, 1.05 1.54 wt% were selected was performed both experimental production condition X70 linepipes. As a result, 1.26, 1.44 1.67 obtained respectively. Metallographical examinations using optical scanning electron microscopy showed that, increasing amount metal, decrease grain size all phases (acicular ferrite, primary ferrite aligned second phase). Moreover, expense acicular volume fraction (mostly boundary ferrite) phase decreased. Also, results indicated that higher Mn, strength hardness case impact toughness tensile elongation, an optimum level observed lower highest attributed hardenability thus formation martensite/retained austenite islands carbides coincident sites grains. analyzes more than 1000m length up 1.4wt%, reduced possibility from total percentage 0.005 around 0.001.© 2008 ASME