The role of addition of Ni on the microstructure and mechanical behaviour of C-Mn weld metals

• Main Authors: Vicente Braz Trindade, João da Cruz Payão, Luís Felile Guimarães Souza, Ronaldo da Rocha Paranhos
• Format: Article
• Language: Portuguese
• Published: Universidade Nove de Julho 2007-01-01
• Series: Exacta
• Online Access: http://www.redalyc.org/articulo.oa?id=81050119

The aim in this work is to study the influence of nickel content (as-welded state and after stress relief heat treatment) on the microstructure and toughness of CMn weld metals obtained with submerged arc welding. The nickel content vary between 0.50 wt.% and 3.11 wt.%. The microstructures were observed using optical microscopy (OM) and scanning electron microscopy (SEM). The toughness was evaluated by Charpy-V impact testing in samples cut transversally to the weld bead. The impact energy showed that nickel content up to 1 wt.% improves the toughness due to the increase of the acicular ferrite (AF) content and microstructural refinement. On the other hand, higher nickel contents have a deleterious effect on the toughness due to the presence of the microconstituent martensite- austenite (M-A) in the weld metal. The stress relief heat treatment did not improve too much the weld metal toughness, even the M-A suffering decomposition (ferrite+carbide). This may be explained by the precipitation of carbides along the boundaries of the ferrite.