Page 245 - Handbook of Structural Steel Connection Design and Details

Welded Joint Design and Production

230 Chapter Three

3.7 Welding Cost Analysis

Welding is a labor-intensive technology. Electricity, equipment depre-
ciation, electrodes, gases, and fluxes constitute a very small portion of
the total welding cost. Therefore, the prime focus of cost control will
be on reducing the amount of time required to make a weld.
The following example is given to illustrate the relative costs of
material and labor, as well as to assess the effects of proper process
selection. The example to be considered is the groove weld of beam
flange-to-column connections. Since this is a multiple-pass weld, the
most appropriate analysis method is to consider the welding cost per
weight of weld metal deposited, such as dollars per pound. Other
analysis methods include cost per piece, ideal for manufacturers asso-
ciated with the production of identical parts on a repetitive basis, and
cost per length, appropriate for single-pass welds of substantial
length. The two welding processes to be considered are shielded metal
arc welding and flux-cored arc welding. Either would generate high-
quality welds when properly used.
To calculate the cost per weight of weld metal deposited, an equa-
tion taking the following format is used:

electrode cost labor overhead rate
Cost per weight
efficiency (deposition rate)(operating factor)
The cost of the electrode is simply the purchase cost of the welding con-
sumable used. Not all of this filler metal is converted directly to deposited
weld metal. There are losses associated with slag, spatter, and in the case
of SMAW, the stub loss (the end portion of the electrode that is discarded).
To account for these differences, an efficiency factor is applied. The follow-
ing efficiency factors are typically used for the various welding processes:

Process Efficiency, %
SMAW 60
FCAW 80
GMAW 90 (CO shielding)
2
98 (mixed gas)
SAW 100 (flux not included)

The cost to deposit the weld metal is determined by dividing the
applicable labor and overhead rate by the deposition rate, that is, the
amount of weld metal deposited in a theoretical, continuous 1 h of
production. This cannot be maintained under actual conditions since
welding will be interrupted by many factors, including slag removal,
replacement of electrode, repositioning of the work or the welder with
respect to the work, etc. To account for this time, an “operating factor”

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