Influence of filler wire composition on weld microstructures of a 444 ferritic stainless steel grade

Vincent Villaret (1) , Frédéric Deschaux-Beaume (1) , Cyril Bordreuil (1) , Sébastien Rouquette (1) , Corinne Chovet (2)

1 AS - Assemblages Soudés
2 CTAS - Centre Technique des Applications du Soudage

Seven compositions of metal cored filler wires for Gas Metal Arc Welding (GMAW), containing the same weight percent of chromium (Cr) and molybdenum (Mo) as 444 steel, but with different titanium (Ti) and niobium (Nb) contents were investigated. Experimental results pointed out that the filler wire Ti content required to be twice time more than the amount expected in the deposited metal. This was due to the low Ti transfer ratio during arc welding. Moreover, Ti increased the wetting angle and promoted penetration. It was supposed that Ti affected the weld pool surface tension what led to inward Marangoni convection. Columnar to equiaxed grain transiton (CET) was also promoted thanks to the precipitation in the weld pool of Ti rich refractory compounds which act as heterogeneous nucleation sites for equiaxed grains. A minimum 0.3% Ti was required in the filler wire to form a completely equiaxed grain structure in the fusion zone. Niobium in the filler wire did not seem to have any effect on penetration, wetting and grain structure of the fusion zone.

Mots clés: columnar to equiaxed transition; grain structure; fusion zone; ferritic stainless steel; GMAW; filler wire

Domaines: Génie mécanique [physics.class-ph]; Génie mécanique [physics.class-ph]; Matériaux et structures en mécanique [physics.class-ph]; Matériaux et structures en mécanique [physics.class-ph]

Vincent Villaret, Frédéric Deschaux-Beaume, Cyril Bordreuil, Sébastien Rouquette, Corinne Chovet. Influence of filler wire composition on weld microstructures of a 444 ferritic stainless steel grade. Journal of Materials Processing Technology, 2013, 213, pp.474-483. ⟨10.1016/j.jmatprotec.2013.03.026⟩. ⟨hal-00825145⟩