©
COPYRIGHT 2000 THE ESAB GROUP, INC. LESSON
IX
ESTIMATING AND COMPARING WELD METAL
COSTS 9.1 INTRODUCTION
Estimating the costs of depositing
weld metal can be a difficult task because of the many variables
involved. Design engineers must specify the type and size of weld joint
to withstand the
loads that the weldment must bear. The welding engineer must select the
welding process, and
type of filler metal that will provide the required welds at the least possible
cost. With wages
and the cost of operations rising, selection of the process that deposits weld
metal most expediently
must be carefully considered. Labor and overhead account for approxi-
mately 85% of the total welding cost.
9.1.0.1 Welding
costs may be divided into two categories; the “fixed” costs involved
regard- less of
the filler metal or welding process selected, and those related to a specific
welding process.
Fixed costs entail material handling, joint preparation, fixturing, tacking,
preheating, weld
clean-up and inspection. Although some of these items will be affected by
the process and
filler metal chosen, they are a necessary part of practically all welding operations.
Calcu- lating
these costs is best left to the manufacturer since they will depend upon his capabilities
and equipment. The cost of actually
depositing the weld metal however, will vary considerably
with the filler metal and welding process
selected. This cost element is influenced by the user’s
labor and overhead rates, deposition rate and efficiency of the filler metal,
operating factor,
and cost of materials and power. 9.1.0.2
This lesson will cover cost estimating
for steel weldments produced by the four most common
arc welding processes in use today: shielded metal-arc welding, gas metal-arc
welding, flux cored arc welding and
submerged arc welding. Gas tungsten arc welding will not
be considered here because the variables,
such as deposition rate and efficiency, are depen- dent
on operator technique, stub use, etc. The GTAW process is a relatively costly
method of depositing
weld metal, and is usually chosen for weld quality or material thickness and compo-
sition limitations, rather than economy.
9.1.0.3 Large
firms will frequently conduct their own deposition tests and time studies to
determine welding costs, but many smaller
shops do not know the actual cost of depositing weld
metal. 9.1.0.4
In estimating welding costs, all attempts
should be made to work with accurate data, which
in some cases is difficult to secure. For this reason, this lesson contains
charts, graphs
