Page 218 - Handbook of Structural Steel Connection Design and Details

Welded Joint Design and Production

Welded Joint Design and Production 203

penetration beyond the root is impossible with visual inspection.
Fusion to the root, and not necessarily beyond, ensures that sufficient
strength is generated, provided the weld is properly sized. While pen-
etration can be verified with ultrasonic inspection, fillet welds rou-
tinely receive only visual or magnetic particle inspection. Thus, no
penetration beyond the root is required, nor is design credit given to
deeper penetration in fillet welds if it happens to be present. Figure 3.17
illustrates this requirement.
The out-of-position capability of a given welding process refers to
the ability to deposit weld metal in the vertical or overhead positions.
It is generally more economical to position the work in the flat and
horizontal positions. However, this is usually impossible for field erec-
tion, and may be impractical under other conditions. The ability to
obtain high travel speeds is important for small welds. It may not be
possible for a high-deposition welding process to be used at high travel
speeds. The size of the droplet transferred, puddle fluidity, surface
tension, and other factors combine to make some processes more
capable of high travel speeds than others.

3.4.2 Process capabilities
After the joint is analyzed and specific requirements determined,
these are compared to the capabilities of various processes. The
process with capabilities most closely matching the requirements typ-
ically will be the best and most economical option.
Submerged arc welding and electroslag/electrogas welding have
the greatest potential to deliver high deposition rates. Multiple-elec-
trode applications of submerged arc extend this capability even fur-
ther. For joints requiring high deposition rates, submerged arc and
electroslag/electrogas welding are ideal processes to contribute to
low-cost welding. When the specific conditions are not conducive to
SAW but high deposition rates are still required, flux-cored arc weld-
ing may be used. The larger-diameter electrodes, which run at higher
electrical currents, are preferred.
Deep penetration is offered by the submerged arc-welding process.
While electroslag/electrogas also offers deep penetration, the joints
on which the electroslag are used typically do not require this capa-
bility. Where open-arc processes are preferred, gas-shielded flux-cored
arc welding may offer deep penetration.
Out-of-position capability is strongest for the flux-cored and shielded
metal arc-welding processes. The slag coatings that are generated by
these processes can be instrumental in retaining molten weld metal
in the vertical and overhead positions. Submerged arc is not applica-
ble for these joints.

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