Welding Basics
One of the most useful skills that an owner of older equipment can have
is the knowledge and ability to weld. It seems like the older
equipment can do a job, albeit slowly compared to newer stuff, but it
tends to break more often. Many of the breakdowns are related to the
implements that are being used: the disc, wagon or bushog are among
them. Knowing how to fix stress cracks, reinforce weak joints by
welding on steel support plates, or cutting and shaping parts and
adapters out of raw steel plating is an asset that is worth its weight
in gold.
For the farm environment there are two types of welding that we will
deal with in this series. Arc welding and oxy-acetylene. The latter
will also include some pertinent information on cutting torches and
fabrication of parts and tools. But we will first cover some basics
dealing with arc welding.
Arc welding is as the name implies, welding with an arc. Simply put, a
positively charged electrode and a negatively charged steel plate
commonly called a ground complete a circuit at the end of a welding
rod. When the rod is held a given distance from the item to be welded
the current jumps the gap creating an enormous amount of heat. The
heat melts the rod end and when the rod is manipulated in a certain
fashion a puddle of liquid metal will result which can be controlled to
make a weld. Of course it is a little more involved than the simple
description above, but the basic premise is that simple; electrical
current jumping an air gap melts the metal.
There are many types of arc welding. A few are carbon-arc,
metal-electrode, gas metal-arc, atomic-hydrogen, MIG, TIG, and many
others. For our purposes we will focus on two basic types of arc
welding; AC and DC. It is difficult to explain the difference in
simple, down to earth terms so lets just settle for some of the main
differences and advantages of each.
AC, or alternating current, is probably the most common and most
economical of welders. A good unit can be purchased at a farm store
for quite a reasonable price. It will do many simple welding tasks
with excellent results. The distinct advantage that AC arc welding has
is that there is virtually no magnetic blow, which causes excessive
splatter and uncontrollable arcs. The basic features are a good
forceful arc, an easy arc to maintain once it is begun, it is great for
heavy steel plating because of deep penetration, and is wonderful for
welding aluminum. The negative factors are that the initial arc can be
difficult to start and that burn throughs on thinner plates of metal
can be a frustrating problem. All in all though, a simple AC welder is
a good all around tool for general repairs.
DC, or direct current, provides for a more variety in welding. Direct
current, by nature, can be manipulated in ways completely different
than the alternating cycles of AC. One example of this is that by
changing the polarity of current flow different welding characteristics
can be realized. Straight polarity, when the current flows from the
rod to the base metal, provides a fairly standard arc for a variety of
metals. Reversed polarity, when the current flows from the base metal
to the rod, provides for 2/3 of the total heat to be centralized in the
welding rod tip. This superheats the electrode metal and shielding gas
from the flux causing the molten metal to travel at a high velocity
resulting in very deep penetration to the base metal. These variations
in the types of DC units can accommodate welding on thick or thin
metals. This can give quite a bit of flexibility when trying to avoid
burn throughs with thinner base metals or working on deeper weld
penetration on thicker plates.
As with any trade there are certain hazards which must be addressed
when arc welding.
1. Avoiding radiation from the arc, ultraviolet and infrared rays
2. Flying sparks, globules of molten metal
3. Electrical shock
4. Fumes
5. Burns
Protective clothing and specialized eye protection must be used in
order to reduce these risks. An arc-welding helmet with protective
lens reduces the amount of harmful eye radiation and protects the head
from splatter and heat. The hair, hands, arms and other skin surfaces
must be covered, preferably with heavy leather to shield out other
harmful radiation produced by the intense arc. Don't wear regular
coverings like heavy cotton or wool as arc welding is accompanied by
flying sparks and molten metal pieces that will ignite such clothing.
Also avoid pants with cuffs, tennis shoes, thin gloves, and shoes with
thin soles.
Avoid electrical shock by working on a dry floor with thick rubber
shoes and by wearing dry leather welding gloves. Also make sure to use
insulated electrode holders and have the equipment properly grounded.
Keep the area properly ventilated to avoid inhaling the burnt fumes.
The fumes generated in the welding process may contain highly toxic
metal oxides. Keep in mind that you are welding with molten metal.
The arc is hot, the metal is hot, and everything in contact with the
metal is hot. Watch for falling metal globules; they burn quickly
through tennis shoes and unprotected pants. When done welding use
tongs to pick up the metal; it does not cool quickly and even when
quenched in water beware of the superheated steam it produces when
dipped and the heat it retains when removed.
Above all be aware of others around you. When an arc is struck to
start welding the sudden flash can cause severe eye damage to
onlookers. Continued observation will quickly cause irreversible
blindness. Keep people away from the project. Protect them as well as
yourself.
Welding Basics, Part 2
Welding, Settings and Electrode Types
We are still dealing with arc welding on our broken bushog in this
series. Our welder of choice for this project will be an AC arc welder
since it seems to be relatively common on farm sites and will also give
us the heat we need for a good penetrating weld. We've also amassed
our protective gear and decided on our location for work. The
onlookers have been chased away for their own protection. So what else
do we need to know before we start welding?
I suppose we should probably take a look at the electrodes, or welding
rods, and see what they are all about. The welding rod is where the
action takes place. This is where the heat is concentrated, the puddle
of metal is manipulated, and the repairing weld is created.
Professional welders consider many factors when picking out a rod for a
job. The types of material being welded play a large part in this
choosing process. Is the metal a mild, low alloy, or nickel steel?
Does it have other melted components like chromium, manganese, or
vanadium in it? Is it aluminum, copper mix bronze or lead? There are
almost too many types of metals to choose from, each using a different
rod to ensure proper metal bonding. So for our bushog repair we'll
just settle for a mild steel type of rod.
Next we have to have a basic understanding of what all those gazillion
numbers imprinted on the rod mean. Most rods that one runs across at
the farm supply store will be labeled something like this: E 6011
or, perhaps, E 7020. The 'E' means that it is an electrode suitable
for arc welding. The following two numbers indicate the tensile
strength of the material in the rod when the weld is stress relieved.
'60' stands for 60,000 psi, '70' for 70,000 psi, etc. The next number,
a one, two, or three, indicate the position of the joint the electrode
is designed to weld. For example, an electrode numbered XX1X will weld
in all positions. A XX2X will weld butt and fillet joints in the flat
or horizontal position. XX3X is recommended for flat position welds
only. The last number is an indicator of the power supply, type of
covering, type of arc penetration and presence of iron powder. Once
again, since thoroughly understanding all these numbers, metal types,
and flux compounds won't get our bushog repaired we'll simply settle
for some general guidelines.
1. A 60XX rod will be easy to find at our supplier and will work great
for our mild steel application.
2. Since cracks rarely stick to flat surfaces we will opt for a
multipositioning rod, XX1X
3. The fourth number, XXX1 will provide us with an arc stabilizer
which will give us AC capabilities.
4. Our rod selection should be E 6011 for our bushog repair.
Now that we've selected our welder, our safety equipment, and rod lets
get an idea of the current level to use. The thickness of the metal to
be welded and the diameter of the corresponding rod will pretty much
determine the amperage setting. Pick out a rod that is about the same
size as the metal. An 1/8 inch rod will have a setting between 30 and
80 amps. The higher the setting the more heat generated; consequently,
the weld will have to be faster or the metal will burn out; there may
also be more splatter to contend with. The lower the setting the more
sluggish the arc will be, there will be poorer weld penetration, and
the arc may flame out more often. Experimenting on a piece of scrap
metal will help determine the setting you are most comfortable with.
If you are using a 3/16 inch rod the settings can be between 100 amps
and 200 amps. Again, it is determined by the welders skill and comfort
in performing his work.
Metal preparation is the key to making a good weld. The surfaces must
be clean of rust, dirt, grease and grime. Grabbing that wire brush and
scrubbing away like brushing your teeth will go a long way to cleaning
the area to be worked on. If there is a stress crack which is being
welded take a hand grinder and grind a 'V' the length of the crack in
order for the weld to penetrate both sides of the break. After each
pass chip off the slag and debris and wire brush the area before
another weld is made. Cracked areas hiding under splatter, rusty metal
flakes and/or layered metallic garbage should have the debris ground
off so the weld will be made against the parent metal or the most basic
of structure. If there are multi levels of paint on the piece then
take a grinder and work out the paint so the arc will strike easier and
so the weld will have better integrity.
One last note, when the final weld has been cooled and the slag and
debris cleaned off of it inspect it carefully to make sure it did what
you wanted it to. Look for undercutting of the parent metal as this
can form a weak spot in the repair. Make sure you followed the crack
and didn't wander off to the side in the excitement of keeping a good
arc and metallic bead. Check to make sure there is ample bead on the
repair and that any repair plates have good penetration on their edges.
Finally drop a good coat of primer and paint on the repair to protect
the bare metal from the elements. Welded repairs seem to rust quicker
than any other type of exposed metallic areas. Besides a good coat of
paint will look good and make the repair look complete.
Welding Basics, Part 3
Oxy-acetylene Welding - Part One
In our series on welding we have taken a brief look at AC and DC arc
welding along with basic techniques and safety equipment required for
safe usage. Since our premise is to cover welding types that might
best be used on a farm environment we have kept our overview
purposefully simple and general.
The second type of welding that this observer finds quite useful in
working with older equipment on the farm is that of oxy-acetylene
welding. Commonly called gas welding it can readily be used for
repairing lighter gauge steel as found on body parts or exhaust systems
along with difficult to repair delicate parts like dash parts and
special light weight holding devices. Let’s take a brief overview of
oxy units and their usefulness on the farm.
The term ‘gas welding’ is not really limited to the use of oxygen and
acetylene. By definition it is the burning of a gas flame, such as
natural gas, LP, hydrogen or acetylene, in the presence of an oxygen
source either from natural air, compressed air or pressurized pure
oxygen. For our purposes it is most convenient to focus on acetylene
gas and pressurized pure oxygen as our gas source since it gives us the
hottest flame capable of melting the common metals encountered on the
farm.
Our term ‘gas welding’, therefore, is the art of joining various metals
together by melting and fusing their adjoining surfaces by using an
intense, concentrated gas flame as the heating medium.
Let’s take a quick look now at the equipment involved with an
oxy-acetylene setup. The most obvious items noticed are the tanks that
store the two gases. It should always be remembered that the
pressurized oxygen and acetylene tanks are to be respected and taken
care of. They can be quite lethal if dropped or misused. The
acetylene tank is usually the smaller and chunkier of the two tanks.
Acetylene gas is highly unstable at pressures over 15 psi so it is
stored in an unusual manner. The stubby tank contains an inert
substance like fullers earth or lime silica, which absorbs acetone.
The acetone absorbs the acetylene and kind of keeps it in suspension
preventing accumulating pockets of high-pressure gas thus stabilizing
the explosive tendencies of the gas. Be careful not to lay the tanks
on their side as this will permit some of the acetone to enter the
valves, lines, and gauges and contaminate the system. A purplish flame
color at the torch is an indication of this contamination. Also note
that the shutoff valve on the acetylene tanks have left handed threads
so the appropriate regulator and corresponding hardware can be properly
installed. It is recommended that this valve only be opened an average
of one half turn when in use so it can be quickly turned off in case
of emergency.
The other cylinder in the pair is the oxygen tank. This can almost be
characterized as a loaded bomb. The gas in a fully charged cylinder
has more than one ton of pressure for every square inch of surface
area. The gas is an oxidizer that supports common combustion to the
extreme and will make typical items burn with an unbelievable violence
and intensity. It should be respected as such and measures should be
taken to ensure a secure storage and usage environment. When not in
use with the corresponding regulator the oxygen cylinder, as with the
acetylene tank, has a heavy-duty screw on cap that protects the valve.
It should always be used. In addition the cylinders should always
remain securely fastened to a wall or similar structure to keep them
from tipping over.
Since the various gases are stored at considerably higher pressures
than are used in the welding process a pressure regulating mechanism
must be provided. Pressure regulators that fasten to the respective
cylinders of gas provide this function. They reduce the cylinder
pressure to a working pressure and also maintain a constant gas
pressure at the torch even though the cylinder pressure may vary. Most
regulators are a two-gauge unit, the high pressure or primary gauge
reflecting the cylinder pressure, the low pressure or secondary gauge
showing the delivery pressure to the torch hose. Once again, the
oxygen fittings are right hand thread, the acetylene are left hand
threads. Take care fastening the respective gauges to their cylinders
and hoses. Don’t over tighten and make sure to use the correct wrench
to avoid curling the brass nuts and fittings. Check to make sure the
regulator-adjusting valve is screwed out all the way to prevent
premature charging of the secondary circuit. Charge the gauges by
slowly cracking the cylinder valves open to prevent pinging of the
gauge needles or melting of the seats due to sudden heat compression in
the gauge. Never use any type of oil or grease in conjunction with
oxy-acetylene fittings or related components. Once again, make sure
all tanks are securely fastened to a wall or supporting structure to
prevent them from tipping over. Keep in mind that acetylene gas is
highly unstable at pressures over 15 psi. Make sure the secondary
gauge measuring the acetylene gas going to the torch hosing never goes
over that pressure.
The hoses delivering the gases from the tanks to the torch should be of
a regular welding type. The rubber is designed not to break down by
the respective gases and already has the correct fittings pre-fitted on
the ends. Take care not to kink the hose or step on it as it stretches
across the work area. Also try to protect it from melted metal
globules that are produced in the welding process. Once again the
fittings are either left or right hand threads matching the
corresponding gas used. The hose fittings screw into the respective
left or right hand receptacles of the gas torch.
The torch is where the gases are mixed and delivered to the torch tip
where they are ignited and used for welding purposes. The gases are
directed into the torch base and through respective shut off valves.
These valves serve two purposes: one for shutting off and on the gas
stream the other for throttling the gas flow to give the flame the
correct characteristics for proper burning. From the valves the gases
flow into the main body of the torch and into the mixing chamber. Then
on through the torch barrel to the tip where it is expelled through a
drilled hole called the orifice. The orifice size depends on the type,
and thickness of metal being welded along with the rod diameter and
heat/pressure requirements. Keeping the orifice cleaned and free of
welding debris will assure a clean and properly formed flame.
As with any welding proper safety gear should be mentioned before the
welding procedure takes place. Make sure and wear the correct
protective eyewear. The flame and puddle of molten metal emits both
ultraviolet and infrared rays that may cause eye injury if viewed at
close distance. The goggles also protect the eyes from flying sparks
and the occasion popping of overheated metal. Generally speaking the
thicker the metal to be welded and the more heat produced by the torch
requires a darker shade for eye protection. A number of 4-5 is a good
all around shading for the casual gas welder. Protective clothing
consists of heavy leather gloves with a gauntlet covering the wrists, a
non-flammable shirt or jacket and flame resistant trousers without
cuffs. Good heavy leather shoes with thick soles will award a little
more time if one accidentally steps on a hot piece of metal. Also be
aware to not wear accessories like pens and other pocket items on your
person when welding. A carefully misplaced spark in an oxygen rich
environment might cause a quick burn scenario that could create a
potential problem. Acquire and use a flint and steel lighter for
igniting the torch. The steel cup tends to trap a small amount of gas
that quickly and safely ignites when sparked.
We’ve taken some time to give a brief overview of the oxy-acetylene
welding unit and offered some safety advice. In the next part of this
series we will look into the welding process and finish up with a few
tips on using the cutting torch.
Welding Basics, Part 4
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
for.
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
thickness’ 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.