LESSON VII ©
COPYRIGHT 2000 THE ESAB GROUP, INC. 7.3.2
Slag
Systems
- The ingredients in the core determine the weldability
of the electrode
and the mechanical properties of the weld metal. Electrodes that have a
prepon- derance
of flux components of an acidic nature produce an acid type slag. Those
elec- trodes that
are composed of larger amounts of components of a basic nature are said to
produce a basic type slag. Electrodes
produced with an acid slag system have excellent weldability.
This means that the arc is smooth and spray-like with very little spatter,
and these electrodes
have high operator appeal. The mechanical properties are good and
meet or exceed AWS specifications.
7.3.2.1 Electrodes
having a basic slag system produce weld metal with excellent ductility
and notch toughness. The weldability
is not as good as that of the acid slag types. Metal
transfer is more globular, resulting
in a bit more spatter. Figure 3 shows the characteristics
of the two slag systems.
7.3.2.2 Some
low alloy electrodes are now being produced utilizing a recent develop-
ment in slag systems, that combines
the excellent weldability of the acid slag types with the
excellent mechanical properties of
the basic slag types. 7.4 GAS
SHIELDED TYPES Gas
shielded flux cored electrodes are available in diameters of .035" to 1/8" and
utilize reverse
polarity (electrode positive) welding current, resulting in high deposition rates,
deep penetration,
and a relatively smooth arc. High deposition rates mean that the weld metal
can be deposited more quickly, saving
labor and overhead costs, the largest part of the total
welding cost. 7.4.1
Joint
Design -
Another factor that influences the cost of deposited weld metal is
the joint design. Figure 4 shows
the single-vee joints suggested by the American Welding Society
for producing sound welds with the least amount of weld metal for the SMAW and
SLAG MECHANICAL
SYSTEMS WELDABILITY
PROPERTIES
Acid Excellent
Good
Basic Fair
Excellent
Rutile Basic Excellent
Excellent SLAG
SYSTEM CHARACTERISTICS FIGURE
3
