LESSON VII ©
COPYRIGHT 2000 THE ESAB GROUP, INC. 7.3 FEATURES
OF FLUX CORED ELECTRODES Flux
cored electrodes combine the advantages of several of the welding processes we
have discussed earlier. As with
coated electrodes, the flux improves the weld metal chemi-
cal composition and mechanical properties.
As in gas metal arc welding and submerged arc
welding, productivity is increased because the electrode is continuous.
7.3.0.1 Flux
cored electrodes may be used for welding carbon steels, low alloy high
strength steels, and the high strength
quenched and tempered steels. They are also used for
welding stainless steels and abrasion resistant steels. These will be covered
in subse- quent
lessons. 7.3.1
Functions
of the
Flux Ingredients
- As with coated ingredients, each manufac-
turer has his own formulas for the
flux ingredients. The composition of the flux core can be
varied to provide electrodes for specific
applications. 7.3.1.1
The basic functions of the flux ingredients
are: a)
Deoxidizers
and Denitrifiers
- Since nitrogen and oxygen can cause porosity or
brittleness, deoxidizers such as manganese
and silicon are added. In the case of self-shielded
electrodes, denitrifiers such as aluminum are added. Both help to
purify the weld metal.
b) Slag
Formers -
Slag formers such as oxides of calcium, potassium, silicon or so-
dium are added to protect the molten
weld puddle from the atmosphere. The slag aids
in improving the weld bead shape and “fast freezing” slags help hold
the weld puddle
for out-of-position welding. The slag also retards the cooling rate, especially
important when welding the low alloy
steels. c)
Arc
Stabilizers -
Elements, such as potassium and sodium, help produce a smooth
arc and reduce spatter.
d) Alloying
Elements -
Alloying elements, such as molybdenum, chromium, carbon,
manganese, nickel, and vanadium, are
used to increase strength, ductility, hardness and
toughness. e)
Gasifiers
- Minerals, such as fluorspar and limestone, are usually
used to form a shielding
gas in the self-shielded type wires.
