The Haynes Welding Manual - VolksPage.Net

Welding with filler rod
Let's say that you need to join two pieces of 1/8-inch-thick metal in a straight
bead from right to left. Position the two pieces such that they are butted together
where they are to be joined, and that you have something blocking or clamping
them in place so they won't move as you weld. Start your weld puddle at the
right end of the seam, and as the puddle develops, use your left hand to insert
the tip of the filler rod into the center of the hot puddle, then pull it out right away.
Set up a rhythm of alternately putting in the rod and taking it out as the bead progresses
to the left. When we describe the puddle, the edge of the puddle closest
to the direction you are traveling is the front edge, while the part of the puddle
you just finished is the rear.
If you have ever done any soldering, you may have a bad habit of heating the
solder with your torch or soldering iron and letting the molten lead drip onto the
joint. This is a bad habit and one you shouldn't bring with you in your welding
practice. The molten puddle should melt the filler rod, not the torch. If the rod
sticks, then you are not keeping the puddfe molten enough, or you are adding
filler rod too fast, either of which will result in a low-quality weld.
This skill of making a good bead, with evenly overlapping ovals and good
penetration will take considerable practice, but if you learn two-handed gaswelding
techniques well, any other welding system you pick up later on will be
considerably easier to learn. Most of the welding you will do will be forehand
welding, in which you angle the torch so that the flame is aimed somewhat toward
the direction of the desired weld bead. This preheats the metal as you go
and makes addition of filler rod to the front edge of the puddle easier because it
is truly hot. Sometimes it seems like keeping the proper torch distance, moving
at the right speed, circling or ovaling the tip and dipping the rod in at the right
time is just too much to concentrate on at one time, but you will get the hang of
it. This isn't "brain surgery" and millions have learned before you. After a good
long practice session, begin to examine things around you that are of welded
construction and you'll get an appreciation of the practice it took to lay down
those beautiful beads that look like they were done by some machine instead of
human hands. Indeed there are some kinds of welding that are done with largely
robotic welding machines, but a good weldor can make virtually perfect joints
that are stronger than the parent metal.
We mentioned before that cleanliness is critical in making good welds. The
two edges to be joined need to be sanded or ground clean to bright metal and
should fit as closely as possible. Small gaps are inevitable
in some kinds of work and can be bridged with filler rod, but
gaps should be kept to a minimum. On thicker materials,
you will find that it is easier to make a clean weld with good
penetration if the edges of the two pieces are beveled before
you weld. This can be done with a file or grinder. Thin
materials have their own idiosyncrasies, mostly to do with
keeping the two edges in alignment. As you progress with
your weld bead, more and more heat travels out into the
parent metal, so that after welding for some distance, the
metal you now encounter is hotter than the metal you
started on, so you may have to adjust the torch away
slightly to compensate for the puddle forming faster.
Another problem with thin materials is that the parent
metal tends to distort with the application of heat. Metal expands
when heated, and two edges that were parallel when
you started welding probably won't stay that way. Usually,
the edges pull away and you have a gap to bridge that wasn't
there when you started. The solution is to tack-weld at
intervals before applying too much heat. A tack-weld is
Gas welding/cutting
3.26 When practicing basic butt welds, tack the near corner
first, then tack the top corner with a slight gap between the
parts. This will close up as the plates grow from welding heat.
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