An Introduction To Welding

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Febrianto Gea (183310124)

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Satria Utomo Saragih (183310207)

Shielded metal arc welders (SMAW) / Stick welders

 An example of a stick welder

                                     

             SMAW welding makes use of stick welders, so named because the coated wire welding electrode resembles a stick you might pick up from your lawn. Electric stick welders cost less than other welding systems, but require more practice and skill to master. People who want to begin welding are often short on cash, and may well choose to begin with a stick welder before possibly moving up to a wire feed welder after a few years.

Application

A stick welder is more limited in its applications, but never needs a refill for gas bottles. Just plug in a stick welder, flip its switch, and it will be ready to weld. It also remains ready to go until the next time you use it. Just keep some welding rod stored in dry, low humidity conditions and you will be ready to weld at any time. If yours is a 120 volt welder, you can take it with you to a job almost anywhere, even though it may be limited in welding power. (Actually, a stick welder can cut steel. A small diameter rod is used at high amperage in a sawing motion through the steel. A bed of sand is usually placed below to catch all of the globules of molten metal.)

Stick welding uses an electrode or welding rod. Electrodes have different numbers to describe them. Some weldors like 6013 electrodes; others prefer 7018; and 6011 electrodes are also widely used. Each has different characteristics which make it more suitable for certain applications and less suitable for others. The numbers provide details on the characteristics of each type of electrode, but those details are beyond the scope of this article.

Gas metal arc welders (GMAAW) / MIG (metal, inert gas)

An example of a MIG/wire feed welder

            MIG welders were invented to increase production rates by removing the need to stop and replace a burned electrode. For the beginning, occasional welder; a MIG welder makes learning to weld much easier.

MIG welders, also known as wire feed welders, use a continuous wire electrode on a spool. Rollers in the welder are driven by a motor and feed the wire at a steady rate through an electrode holder, usually called a gun. The fresh weld is protected from the oxygen in the air by being continuously covered with an inert gas. If oxygen comes into contact with the hot, fresh weld; the weld becomes porous and is weakened.

MIG is generally preferred and more expensive than flux core wire feed welding. MIG-capable welders are more costly than flux core welders because they include a gauge for regulating the shielding gas flow, a tube around the gun liner for carrying the gas to the gun, and a solenoid valve to start and stop the gas flow when the arc begins and stops. There is also the cost of the gas and a steel bottle to contain it. MIG welders can be used with flux core wire, but flux core welders cannot be outfitted as MIG welders. The advantage of MIG welders is that the welds have a better appearance and better penetration. There is also less cleanup after welding. But, in windy conditions, the gas that shields MIG welds can be blown away before it does its job.

Application :

Ø    Turn on your wire feed welder and let it run for a minute or so before beginning to weld. You may either push or pull the gun.

Ø  Much of what applies to stick welding practices also applies to welding with a wire feed unit. A steady hand, the correct angle of the electrode holder (stinger or gun), the correct heat setting, the correct travel speed, etc., are all necessary in both processes. However, in stick welding, attention is given to the length of the arc; whereas with wire feed welders, the amount of wire sticking out of the end of the copper welding tip at the end of the welding gun becomes important. See the manual for your welder.

Ø  Wire feed welders are also much easier to use than stick welders. They do not require the same skill level and amount of practice as stick welding. Some say laying a bead with a wire feed welder is like putting down a bead of toothpaste on a countertop; almost anyone can do that. The catch is that it is much more difficult to see where you are welding with a wire feed welder.

Ø  It is not uncommon to wander off of the joint while welding with a wire feed welder. This can be overcome by looking under the gun ahead of where it is welding, as there is enough light from the arc to see a bit of the unwelded joint to use as a guide for the moving gun. That works unless the sun is coming from over the weldor’s shoulder. In that case, the inside of the helmet is bright and one has great difficulty seeing even the arc. An auto-darkening helmet is a tremendous help, and well worth the cost.

Ø  In order to be sure your weld has good penetration and is not a “cold weld” (weld material laid over the parent metal without any real bonding), look for blue discolorations in the parent metal on both the left and right sides of the weld as a sign of good penetration.

Ø  When it is time to stop welding with a stick welder, the weldor simply pulls the electrode away from the steel and the arc stops. When using a MIG welder, those who are used to stick welders need to learn to release the trigger on the gun before pulling the gun up and away from the steel. Failure to do this results in a couple of inches of wasted electrode wire sticking out of the gun. This must be trimmed before beginning to weld again.

There are some good videos on YouTube for how to do MIG welding.

When to replace the wire feed’s tip

In time, the hole in the tip wears and exactly where the wire will strike the metal when the trigger is pulled becomes less predictable. When you notice this unpredictability, it is time to replace the copper tip.

Flux cored arc welders (FCAW)

Flux cored welders use a thin wire electrode that has a chemical powder in its center. This powder melts and flows over the weld to protect the fresh weld from oxygen. This hardened coating is called slag. After the weld cools, you can chip or brush it off, depending on how thick it is. With a flux core welder, one can sometimes begin a new weld without trimming the burned end, but there are other times when an arc will not begin without first trimming the wire to make a fresh new end.

Whereas MIG welding requires very clean steel, flux core welders can dig through some surface impurities to make a good weld. Flux core welders can also be used in windy conditions with no problems.

Gas tungsten arc welding (GTAW) / TIG (tungsten inert gas) welding

TIG welders use a torch with a sharp tungsten tip to make a pool of molten metal with an arc. The operator dabs metal from a thin wire rod into the pool. At the same time, the operator increases or decreases current to the arc with a foot pedal control.

TIG welding makes beautiful welds on aluminum and various special metals. It requires much skill and practice to master.

Gas welders

Oxy-acetylene (gas) welders use two tanks, one filled with oxygen and the other with acetylene. Both gases flow through hoses at controlled pressures to mix and burn with a very hot pointed flame in a torch. A gas welder can cut steel, heat steel for bending as if it were a piece of soft wire, and weld or braze.

Handy Terminology

Penetration

Penetration means the welder did not merely lay a bead of welding material over the top of a joint, but some of the parent metal melted and fused together below the weld, too.

Weaving

Weaving is moving the arc from one side of the joint to the other in order to make certain the weld penetrates into both sides of the joint. A weaving pattern is also used to prevent sag when welding in an upward direction on a vertical joint.

Sag

Sag is molten metal that flows out of the joint while welding due to the effects of gravity. This can be a problem when the weld is vertical, overhead, or horizontally along the side of a vertical surface. Avoiding excess heat, using electrodes designed to harden quickly, fixing the angle at which the arc is directed, and general manipulation of the arc may be used to counteract sag.

Welder vs. weldor

Technically, a welder is the equipment used to make welds, i.e. the welding machine. A weldor is the individual who uses a welder to make welds. Often “welder” is used for both.

Educational resources

If you buy a new welder, it will come with a thin manual that covers safety, some mechanical information about the welder, and a few basic welding procedures to get you started.

If you buy a used welder without a manual, you can probably download a manual for it, or a manual for a similar machine. There are many aids available for the person who wants to learn to weld. Some are in text (either electronic or on paper), while others are videos. There are numerous video tutorials on all aspects of welding on YouTube. Some are done well; others are rather poor.

Safety

Ventilation

Electric welding rods produce toxic fumes. Have a fan nearby, and stand near the open garage door. Galvanised steel also makes fumes you do not want to breathe. Grind the zinc coating away before welding and use good ventilation.

UV burns

Cover your exposed skin. Arc welding generates UV rays linked to skin cancers. Resist the temptation to peak out from under the welding helmet in order to see while striking the arc. Instead, use a piece of carbon rod.

An example of a UV burns