-4- ©
COPYRIGHT 2000 THE ESAB GROUP, INC. LESSON
IX
9.2.4
Deposition
Efficiency - Deposition efficiency is the relationship of
the weight of the
weld metal deposited to the weight of the electrode (or wire) consumed in making
a weld. It can
be accurately determined only by making a timed test weld, and carefully weighing
the weldment and
the electrode or wire, before and after welding. The efficiency can then
be calculated
by the formula: Deposition
efficiency = Weight
of Weld Metal ÷ Weight of Electrode
Used (or)
Deposition Rate (lbs/hr) ÷
Burn-off Rate (lbs/hr) 9.2.4.1
The deposition efficiency tells us
how many pounds of weld metal can be expected from
a given weight of the electrode or welding wire purchased. As an example,
100 pounds of
a flux cored electrode with an efficiency of 85%, will produce approximately 85
pounds of weld
metal, while 100 pounds of coated electrode with an efficiency of 65%, will produce
approximately 65 pounds of weld metal,
less the weight of the stubs discarded, as described below.
9.2.5
Coated
Electrodes - The deposition efficiency
of coated electrodes by AWS definition,
and in published data, does not consider the loss of the unused electrode stub
that is discarded.
This is understandable since the stub length can vary with the operator
and the application.
Long continuous welds are usually conducive to short stubs while on short
inter- mittent
welds, stub length tends to be longer. Figure 3 illustrates how the stub
loss influences the
electrode efficiency when using coated electrodes. 9.2.5.1
In Figure 3, a 14” long by 5/32”
diameter E7018 electrode at 140 amperes is con- sidered.
It is 75% efficient, and a two inch stub loss is assumed. The 75%
efficiency applies FIGURE 3
DEPOSITION EFFICIENCY = 75%
actual efficiency, including stub loss
= 9 ÷ 14 = 64.3% 12"
LENGTH OF ELECTRODE CONSUMED AMOUNT
THAT BECOMES WELD METAL (LENGTH
CONSUMED X EFFICIENCY) 14"
LOST TO SLAG,SPATTER
& FUMES 2"
STUB LENGTH
9"
