Until the end of the 19th century, the only welding process was forging welding, mainly by blacksmiths, which had been used for centuries to join iron and steel by heating and hammering.
Resistance welding appeared in the late 19th century. During the 20th century, especially after World War I, welding methods advanced rapidly, due to the demand for a reliable and inexpensive welding method. The most significant leap occurred during World War II, when MMA welding was invented, which is electrode welding.
The welding operation
Welding is a physical process of joining two metal bodies by melting part of both bodies, sometimes adding additional metal, and re-solidifying after cooling.
There are three forms of welding:
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- Electric arc
- Electric current
- Change of accumulation status
Welding methods differ from each other in the heating method, and in the question of whether a third material is added to the welded bodies. The third material is also called a “filler material”, and in some welding methods it constitutes the body.
The electrode
The electrode, at its core, is an electrical conductor.
The concept was coined by Michael Faraday (an English physicist and chemist), from the combination of the word electron with the word “hodos” – a path in Greek.
The electrode itself contains a core wire (metal), coated with a ceramic layer, on which is a chemical coating (CO2).
Generally, a 2.5 mm electrode will suffice for basic welding.
There is a direct relationship between the thickness of the electrode and the material being welded.
Electric arc welding methods
SMAW – Shielded Metal Arc Welding Welding using a coated electrode that creates an electric arc.
TIG – Tungsten Inert Gas Welding using a tungsten electrode that creates an electric arc protected by ionized argon gas, with the filler material being fed from the side, usually manually by the welder. Because of the use of a gas to shield against oxygen, the filler material is not coated.
MIG – Metal Inert Gas Welding using a metal electrode and an electric arc. The electrode constitutes the filler material, and is fed to the welding point mechanically by the welder herself.
Welding using an electrode
SMAW – Shielded Metal Arc Welding Welding using a coated electrode that creates an electric arc. During welding, the coating releases a gas that protects the liquid weld spot from oxidation.
The electrode body itself is melted during welding and added as a third material to the welded bodies.
The electrode coating is also melted, coating the welding area. After the bodies have cooled and solidified, it is customary to remove this coating (known colloquially as “slag”), using a special hammer known as a “slag hammer.”
Protection against oxidation is essential, because excess oxygen in the joint area will cause a weak seam.
The welder and her role
The welder receives electrical current (AC), which moves in cycles of 50-60 cycles per second (Hz), and converts it to direct current (DC).
Inverter (INVERT).- Converts voltage and multiplies power, and maintains a stable voltage.
The role of the welder is divided into two:
Provide desired voltage/current to the electrode.
Keep the current steady.
The handles
“Gripping” handle – holds the electrode.
Ensures a quality stream.
“Crocodile” handle – closes a circle.
The length of the handles – depending on the required amperage.
Additional concepts in welding
HOT START – A device that provides “excess voltage” to maintain correct voltage whenever welding restarts.
ANTI STICK – cuts off current in the event of the electrode sticking to the material being welded.
ARC FORCE – A factor that allows for an expansion of the welding arc, a greater mass of the electrode, and facilitates the transfer of the molten material between the electrode and the base material.
MIG welding
MIG welding with a CO2 welder is basically similar to electrode welding. The main differences are that there is no electrode here, but a continuous wire that causes an electrical short, and the protection of the weld is done with gas rather than by coating the electrode. This method allows for clean, strong work and the product has a beautiful finish.
Since this welding uses gas, MIG welding must be performed in a closed site, it requires longer professional training and must be organized accordingly, including more sophisticated equipment, since large amounts of heat are produced during the work.
MIG welding how it works
A continuous wire that constitutes the filler material and an electric arc that is introduced through the handle (shielded by argon or CO2 gas) are the basis of MIG welding, which is why a MIG welder is also called a CO2 welder. It can be semi-automatic, so the welder will have to hold the handle, and the wire will be fed by a machine, or fully automatic, for example using a robot.
On the other hand, if you don’t pay attention to the small details, MIG welding can cause a lot of spatter and create a weld with an unaesthetic finish.
Another disadvantage lies in the fact that welding metals of small thickness creates relatively large amounts of heat, light, and distortions, which can make the welding process difficult.
Advantages and disadvantages
Simple to operate compared to other welding methods, and if the gas and electrical directions are carefully adjusted, a variety of metals can be welded, in a wide range of thicknesses and in all positions.
MIG welding using continuous wire will increase productivity and reduce the amount of defects in the welding process.
MIG welding produces little smoke compared to other methods.
Since MIG welding does not have a thick layer of slag, the cleaning process after welding is short and very easy.
MIG welding has many applications, from root welds, filler welds, through welding thin materials (up to 0.6 millimeters) to closing gaps.
TIG welding
Argon TIG welding is considered the highest quality and is similar in many ways to the MIG welding method. It is characterized by strength and cleanliness, and due to the absence of slag (shellac), it does not require grinding and polishing, which are essential steps in many other types of welding.
The main difference between it and MIG welding is the use of a non-consumable tungsten electrode, which transmits a strong current that creates high heat.
The advantages of this method are the strength of the welds and the level of control the welder has when performing the work.
On the other hand, this method is slower because the welding wire needs to be replaced frequently, it requires a very high level of skill on the part of the welder, and it is more dangerous, due to the high intensity of the light emitted.
Pulse welder
A pulse welder, as its name suggests, works in pulses, releasing a drop of material with each pulse.
Despite the relatively high cost of welding, it is very economical in material and very versatile, and in the long run, is considered more efficient and economical.
You can work with one coil for a wide variety of jobs, due to the ability to work at the extremes of the amp.
The very act of working in pulses reduces splashes and the emission of toxic gases.
