Welding Basics, Part 4|
by Curtis von Fange
Oxy-Acetylene Welding - Part Two
Our ongoing series is discussing some basics in barnyard welding. The
previous article gave some introductory material on the equipment and
safety factors when working with an oxyacetylene unit. This portion
will try to deal with the gas welding procedure and what we can use it
We've been working slowly but surely on our bushog repair over the past
several months. Let's pretend for a moment that our natural talent for
stick welding has surpassed all our dreams and our heavy framing and
reinforcement is complete. Now we need to weld on the sheetmetal so we
can wrap this thing up and paint it. But to our surprise the arc tends
to melt the sheetmetal faster than the metal framework. The difference
in metal thickness makes the thinner metal blow away before a puddle
can be formed. Here is a great example of how gas welding can come in
handy. Let's take a quick review before we start.
Our oxygen and acetylene tank are secured to the wall, stand, or cart
with a chain. The regulators are in the off position or are unscrewed
all the way so no pressure is present on the diaphragm. The hoses are
safely wound away from the weld-site. We have our gloves, goggles,
leather wear, and safety shoes on and our uncoated steel rod is lying
to the side, easily accessible within our reach. The repair has been
wirebrushed and cleaned of debris and is ready to weld.
When gas welding with thin tin like on our bushog we want to keep the
pressures on the regulators quite low so we don't make a blowing flame.
We are also using a smaller orifice on the torch to help keep the heat
level low. In general the thin metal we are welding will require a rod
about the same thickness. If the sheet metal is 1/8 inch in thickness,
then we need a 1/8th uncoated rod. The torch orifice size is equated
to a numbered drill size, in this case a size 54 -57 tip drill size.
The pressures on the regs are low: 5 psi for the oxygen and 5 psi for
the acetylene. Remember these are pressures for gas welding with a
single orifice torch. Pressures for the cutting torch are different
and are not for this type of repair. Remember to open the gas tank
cylinders slowly to prevent regulator damage and then screw down the
diaphragm adjusters to the appropriate pressure settings. It can be
helpful to open the corresponding torch valve at the same time to bleed
the gas in the line off and to ensure the correct gauge setting.
Now we are ready to light up. Open the acetylene torch valve no more
than 1/16 of a turn. Cup the flint lighter over the tip to collect a
little gas and ignite. Next, turn the acetylene torch valve on slowly
until the acetylene flame becomes turbulent a distance of 3/4 inch to
one inch away from the orifice. Note that at this distance the flame
will stop smoking. When proper turbulence is recognized open the
oxygen valve a little bit. Note the color change in the flame and the
slow development of an double inner cone within the acetylene flame.
As oxygen is increased the larger middle flame will merge with the
inner greenish hued cone. When there is only one lightish green/blue
cone established then the flame is called a neutral flame. If the
secondary or middle flame is still visible then the flame is called a
carburizing flame; a cooler flame with too much acetylene is being
consumed. If the inner cone is established and then additional oxygen
is added it becomes an oxidizing flame. This is also characterized by
a hissing sound to the torch and more of a bluish tinge to the flame.
Too much oxygen will burn or oxidize the metal being welded. The
neutral flame has a soft purring sound to the torch, has a well defined
inner cone with the greenish/blue tinge, and is the hottest part of the
flame produced. This is the flame we are looking for.
Next step is to heat the metal we are going to weld. In the case of
our bushog we want to preheat the thickest metal first. Hold the torch
at a 30 to 45 degree angle to the work. The flame spreads over the
work in the direction in which the weld is progressing and acts as
preheater to the material. Rotate the torch tip in a circular motion
for even heating and puddle control; hold the inner cone just above the
developing molten puddle of metal. This motion should be contained
within the parameters of the created molten puddle and not stray
outside the welding area. If the puddle starts to sag or burn through
then adjust the distance of the flame to the weld by increasing the
angle of the flame rather than by pulling the flame away from the
puddle. The molten puddle that you create with the flame is what will
make the weld between the metals. When working with the different
thicknessí of metal it is necessary to form the puddle on the thickest
portion of steel and then float the puddle onto the thinner steel so as
to not burn through. Adding extra metal to the puddle with a rod may
or may not be necessary. If the parent steel is thick enough then the
puddle may flow easily to the thinner steel and form a great weld. If
additional metal is needed then the rod may be added. Move the rod
towards the flame so it is preheated then place the rod end into the
puddle as more metal is required. The flame will melt the rod
accordingly. Try to avoid a dripping rod as this only creates a weaker
weld. As with most things it takes some practice, trial and error.
Take some scrap pieces to practice on before doing a finished job which
will show your skill; or lack thereof.
Here are a couple of tips to keep in mind as you weld. The appearance
of the puddle will be a good indicator as to your progress. A good
puddle will have a smooth, glossy appearance. The edge away from the
torch will have a small bright incandescent spot which will move
actively around the edge of the puddle. If this spot is oversize the
flame is not neutral. If there are weld bubbles and excessive sparks
then there is either a poorly adjusted flame or a poor quality/dirty
metal/rod that you are working with. If the torch pops and spits then
try to increase the pressures in the regulators just a little bit. The
gases are preigniting and may be corrected by a somewhat higher
pressure from both tanks. The tip also may become overheated by
operating it too close to the molten puddle; try extending that
distance. Another possibility of torch popping is that the tip may
have some carbon deposits or hot metal particles in the orifice. Using
a properly sized tip cleaner will open the passage back up. Avoid
submerging the inner cone into the molten metal as this can create a
flashback condition where the gas burns back into the regulator.
All in all the more time spent practicing with the puddle the better
the weld seams that will be produced. Take your time and slowly move
the puddle forward along the metal seams making sure the circular
motion of the torch is consistent. Heat control by this method ensures
that the puddle will not grow out of hand or that a burn through will
result. With a little practice one will find that this type of welding
is real handy when working with thinner metals because it offers quite
a bit of creative control in the weld.
In the last installment of this series we will give some tips and
instruction on using a cutting torch.
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