The　effect　of　inclusions　on　the　microstructure　and　toughness　of　the　deposited　metals　of　self-shielded　flux　cored　wires　was　investigated　by　optical　microscopy,　electron　microscopy　and　mechanical　testing.　The　deposited　metals　of　three　different　wire＇s　showed　different　levels　of　low　temperature　impact　toughness　at　-40　degrees　C　mainly　because　of　differences　in　the　properties　of　inclusions.　The　inclusions　formed　in　the　deposited　metals　as　a　result　of　deoxidation　caused　by　the　addition　of　extra　Al-Mg　alloy　and　ferromanganese　to　the　flux.　The　inclusions,　spherical　in　shape,　were　mixtures　of　Al2O3　and　MgO.　Inclusions　predominantly　Al2O3　and　0.3-0.8　mu　m　in　diameter　were　effective　for　nucleation　of　acicular　ferrite.　However,　inclusions　predominantly　MgO　were　promoted　by　increasing　Mg　in　the　flux　and　were　more　effective　than　Al2O3　inclusions　of　the　same　size.　These　findings　suggest　that　the　control　of　inclusions　can　be　an　effective　way　to　improve　the　impact　toughness　of　the　deposited　metal.　(C)　2015　Elsevier　B.V.　All　rights　reserved.