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7.7 Reducing Dross for Clean Cuts
Dross (slag) is the excess material that spatters and builds up on the underside of the work-piece as you
cut. Dross occurs when the operating procedure and technique is less than optimal. It will require practice
and experience to obtain cuts without dross. Although less than optimal cuts will contain dross, it is
relatively easy to remove by breaking it off using pliers or chipping off with a chisel or scraping or grinding
the finished cut as needed and is generally only a minor inconvenience.
A combination of factors contributes to the build-up of dross. They include; material type, material
thickness , amperage used for the cut, speed of the torch across the work-piece, condition of the torch tip,
input line voltage, air pressure, etc. Generally there is an inversely proportional relationship between
output current and speed of cut. Do not use more output current than is necessary and adjust speed of cut
toward minimizing dross build-up on underside of cut. Experiment with adjusting current and speed to
minimize dross.
When dross is present on carbon steel, it is commonly referred to as either 'high speed', 'low speed', or
'top dross'.
'Top dross' is present on top of the plate and is normally caused by too great a torch to plate distance or
too fast travel speed. It is normally very easy to remove and can often be wiped off with a welding glove.
'Low speed dross' is normally present on the bottom edge of the plate. It can vary from a light to heavy
bead, but does not adhere tightly to the cut edge, and can be easily scraped off.
'High speed dross' usually forms a narrow bead along the bottom of the cut edge and is very difficult to
remove. Usually it will need to be removed by grinding. When cutting troublesome steel, it is sometimes
useful to reduce the cutting speed to produce 'low speed dross'. Any resultant clean up can then be
accomplished by scraping, not grinding.
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© Weldclass 2019 | E.&O.E.
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