Comparison of the effects of fluorides in rutile-type flux cored wire
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Various fluorides, CaF2, Na3AlF6, K2SiF6, MnF3, and MgF2, were added to rutile-type flux cored wires at concentrations of 1.8–2.3% and their effects on hydrogen reduction in weld metals were studied. All the fluorides reduced the hydrogen content but there were differences in the levels of reduction among the wires; CaF2 showed the greatest reduction and MnF3 showed the least. The hydrogen content in the weld metals was not influenced by the fluorine formed in the arc but by the slag basicity due to the small amount of fluorides added. The weld metal with higher slag basicities had a lower hydrogen content. The effects of fluorides on the arc stability, weld metal hardness, and microstructure were also examined. Because of the higher ionization potential of Mn, the wire containing MnF3 had the most unstable arc during welding. The wire containing MnF3 also produced a lower weld metal hardness than the other wires owing to its lower weld metal hardenability due to the greater oxidation loss of the C, Si, and Mn elements during welding.
Keywordsalloys welding hydrogen hardness test fluorides
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