Page 229 - Handbook of Structural Steel Connection Design and Details

Welded Joint Design and Production

214 Chapter Three

Even if prequalified joint details are employed, the welding proce-
dure must be qualified by test if other prequalified conditions are not
met. For example, if a prequalified detail is used on an unlisted steel,
the welding procedures must be qualified by test.
Prequalified status requires conformance to a variety of procedural
parameters. These include maximum electrode diameters, maximum
welding current, maximum root-pass thickness, maximum fill-pass
thickness, maximum single-pass fillet weld sizes, and maximum single-
pass weld layers.
In addition to all the preceding requirements, welding performed
with a prequalified WPS must be in conformance with the other code
provisions contained in the fabrication section of AWS D1.1-98
Structural Welding Code.
The code does not imply that a WPS that is prequalified will auto-
matically achieve the quality conditions required by the code. It is the
contractor’s responsibility to ensure that the particular parameters
selected within the requirements of the prequalified WPS are suitable
for the specific application. An extreme example will serve as an illus-
tration. Consider the following example of a hypothetical proposed
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1
WPS for making a ⁄ 4 -in fillet weld on ⁄ 8 -in A36 steel in the flat position.
The weld type and steel are prequalified. SAW, a prequalified process,
is selected. The filler metal selected is F7A2-EM12K, meeting the
requirements of D1.1-98. No preheat is specified since it would not be
3
1
required. The electrode diameter selected is ⁄ 32 in, less than the ⁄ 4 -in
maximum specified. The maximum single-pass fillet weld size in the
1
flat position, according to D1.1-98 is unlimited, so the ⁄ 4 -in fillet size
can be prequalified. The current level selected for making this particu-
lar fillet weld is 800 A, less than the 1000-A maximum specified.
However, the amperage level imposed on the electrode diameter for
the thickness of steel on which the weld is being made is inappropriate.
It would not meet the requirements of the fabrication chapters which
require that the size of electrode and amperage be suitable for the
thickness of material being welded. This illustration demonstrates the
fact that compliance with all prequalified conditions does not guaran-
tee that the combination of selected variables will always generate an
acceptable weld.
Most contractors will determine preliminary values for a prequalified
WPS based upon their experience, recommendations from publications
such as the AWS Welding Handbooks, from AWS Welding Procedures
Specifications (AWS B2.1), or other sources. It is the responsibility of
the contractor to verify the suitability of the suggested parameters
prior to the application of the actual procedure on a project, although
the verification test need not be subject to the full range of procedure
qualification tests imposed by the code. Typical tests will be made to

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