Dross Formation - ESAB ESP-150 Manual De Instrucciones

SECTION 4

DROSS FORMATION

Cutting speed, gas selection and variations in metal composition contribute to
dross formation. The correct cutting standoff also has an influence on dross for-
mation. If the arc voltage is set too high, the cut angle becomes positive. In addi-
tion, dross forms on the bottom edge of the part. This dross can be very tenacious
and require chipping and grinding for removal. Setting the cutting voltage too low
results in undercutting the parts or negative cut angle. Dross formation occurs but
in most cases it is easily removed.
Top Dross
Top dross usually appears as splatter near the top edge of the kerf. This is a result
of torch standoff (arc voltage) set too high or cutting speed set too fast. Most
operators use the parameter charts for recommended speed. The most common
problem is torch standoff or arc voltage control. Simply lower the voltage settings
in increments of 5 volts until the top dross disappears. If an arc voltage control is
not used, the torch can be lowered manually until the dross disappears.
TOP DROSS:
Splatter appears on the top edge of
both pieces of the plate.
Lower the voltage in increments of 5
volts dc (maximum) until top dross
disappears.
HIGH SPEED DROSS:
Fine roll over dross that welds to
bottom of edge. Cleaning requires
chipping or grinding.
LOW SPEED DROSS
Globular dross that forms in large
deposits. Comes off very easily.
SUMMARY
Arc voltage is a dependent variable. It is dependent upon cutting amperage,
nozzle size, torch standoff, cut gas flow rate and cutting speed. An increase in
arc voltage can result from a decrease in cutting speed, an increase in cutting
amperage, a decrease in nozzle size, an increase in gas flow and an increase in
torch standoff. Assuming that all of the variables are set as recommended, torch
standoff becomes the most influential variable to the process. Good and accu-
rate height control is a necessity in producing excellent cut quality.
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Fig. 23 - Top Dross Formation
Fig. 24 - High Speed Dross
Fig. 25 - Low Speed Dross Formation
OPERATION