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Reactions at the molten flux-weld pool interface in submerged arc welding
In submerged arc welding (SAW) of chromium
(Cr) containing steels, Cr is usually added to the weld
metal from the weld wire, and not from the welding
flux. Manufacturing of weld wires of specific compositions
is expensive and time consuming and cannot closely
match all the desired alloy compositions. Therefore,
the weld wire chemistry is usually over matched to the
base plate composition. Better matching between the
weld metal and base plate is possible if the weld metal
incorporates Cr from Cr containing metal powder, instead
of sourcing Cr from weld wire of limited Cr content.
Because Cr is easily oxidised, the oxygen partial pressure
in SAW must be controlled. This work illustrates the control
of the oxygen potential at the molten flux-weld pool
interface by using aluminium (Al) powder addition. The
controlled oxygen potential at the molten flux-weld pool
interface ensures increased Cr powder transfer into the
weld pool, without interfering with oxygen transfer from
the plasma arc to the weld pool. The objective of this
work is to use targeted powder additions to better control
Cr reactions in SAW to improve Cr metal transfer to the
weld metal and maintain an acceptable level of oxygen in
the weld metal.