Welding Sheet Metal - Lincoln Electric AC-235 Manual

Welding Sheet Metal

Welding sheet metal presents an additional problem. The
thinness of the metal makes it very easy to burn through.
Follow these few simple rules:
1. Hold a very short arc. (This prevents burn through, since
beginners seem to hold too long an arc.)
2. Use 1/8" (3.2mm) or 3/32" (2.4mm) Fleetweld 180 electrode.
3. Use low amperage. 75 amps for 1/8" (3.2mm) electrode,
40-60 amps for 3/32" (2.4mm) electrode.
4. Move fast. Don't keep the heat on any given point too
long. Keep going. Whip electrode.
5. Use lap welds whenever possible. This doubles the
thickness of the metal.
Hardfacing
There are several kinds of wear. The two most often
encountered are:
1. Metal to Ground Wear.
(Plowshares, bulldozer blades, buckets, cultivator
shares, and other metal parts moving in the soil.)
2. Metal to Metal Wear.
(Trunnions, shafts, rollers and idlers, crane and mine car
wheels, etc.)
Each of these types of wear demands a different kind of
hardsurfacing electrode.
When applying the proper electrode, the service life of the
part will in most cases be more than double. For instance,
hardsurfacing of plowshares results in 3-5 times more
acreage plowed.
How to Hardface the Sharp Edge (Metal to Ground
Wear)
1. Grind the share, approximately one inch (25mm) wide
along the edge, so the metal is bright.
2. Place the share on an incline of approximately 20-30°.
The easiest way to do this is to put one end of the share
on a brick. (See drawing.)
Most users will want to hardface the underside of the
share, but some might find that the wear is on the top
side. The important thing is to hardface the side that
wears.
3. Use 1/8" (3.2mm) Abrasoweld™ electrode at 90-105 amps.
Strike the arc about one inch (25mm) from the sharp edge.
4. The bead should be put on with a weaving motion, and
it should be 1/2 to 3/4" (12.7 to 19mm) wide. Do not let
the arc blow over the edge, as that will dull the edge.
(See drawing.)
5. Use the back-stepping method. Begin to weld 3"
(75mm) from the heel of the share and weld to the heel.
The second weld will begin 6" (150mm) from the heel,
the third weld 9" (225mm) from the heel, etc.
Backstepping greatly reduces the chances for cracking of
the share, and it also greatly reduces possible warpage.
NOTE: The entire process is rather fast. Many beginners
go much to slow when hardfacing plow shares, running the
risk of burning through the thin metal.
Hardfacing of Idler and Roller (Metal to Metal Wear)
A very common application of hardfacing for metal to
metal wear is the hardfacing of idlers and rollers and the
rails that ride on these rollers and idlers.
The reason for hardfacing these parts is primarily mone-
tary. A few dollars worth of electrode will completely build
up a roller or idler, and the hard surface will outlast sever-
al times the normal life or such rollers and idlers.
If the following procedure is followed, it is not even neces-
sary to remove the grease bearing while welding. This will
save a lot of time:
1. The roller (or idler) is inserted on a piece of pipe that is
resting on two sawbucks. This enables the operator to
turn it while welding.
2. Use Jet-LH BU-90 electrodes, 5/32" (4.0mm) at 175
®
amps or 3/16" (4.8mm) at 200 amps.
3. Weld across the wearing surface. Do not weld around.
4. Keep the roller (or idler) cool by quenching with water,
and by stopping the welding periodically. This will pre-
vent shrinking of the roller (or idler) on the grease bear-
ing.
5. Build-up to dimension. The weld metal deposited by
BU-90 electrode is often so smooth that machining or
grinding is not necessary.
– 16 –
(12.7 to 19 mm)