What Is Arc Welding & How Does It Work?
What Is Arc Welding?
Arc welding is a welding process that is used to join metal to metal by creating enough heat from an arc that is generated and sustained by an electric current, and the melted metals, when cool, result in a binding of the metals. It is a type of welding that uses a welding power supply to create an electric arc between a metal stick ("electrode") and the base material to melt the metals at the point of contact. Arc welders can use either direct (DC) or alternating (AC) current, and consumable or non-consumable electrodes.
The welding area is usually protected by some type of shielding gas (e.g. an inert gas), vapor, or slag. Arc welding processes may be manual, semi-automatic, or fully automated. First developed in the late part of the 19th century, arc welding became commercially important in shipbuilding during the Second World War. Today it remains an important process for the fabrication of steel structures and vehicles.
That’s pretty broad. So, it’s not surprising to find arc welding includes popular welding processes like stick, MIG, TIG, and flux-cored welding. All use an electric arc to weld.
Notice, this is more than just stick welding. Some use arc welding as slang to refer to stick welding. While it is a form of arc welding, it is not the only one.
How Does Arc Welding Work?
At a very basic level, all arc welders have five components:
1. An Electrode and electrode cable
2. A Ground Cable and Clamp (sometimes called a work cable)
3. A Power Supply
4. Metal workpieces
5. An Arc
Basic Arc Welding Diagram. This is the TIG arc welding process. Note: not all arc welders are stick welders. Read more on the different types below.
The power supply provides AC or DC to create and sustain the arc, and the electrode is either mechanically or manually moved along the joint to create the weld.
So, how hot is a welding arc that melts and fuses metal? About 6,500°F. This does the job of melting and fusing the metal pieces, but it also creates another problem.
At these high temperatures, molten metal can react with gases in the air. This causes problems like porous and weak welds, excessive spatter, and reduced productivity.
To eliminate these welding defects, it is common to provide some form of protection to the molten pool when arc welding. This usually comes in two forms.
One option is a special shielding gas flooded over the hot weld. The type of gas and flow rate must be correct for the shielding gas to keep the atmospheric air away from the molten metal.
The second choice is flux, which creates its own shielding gas and slag when exposed to the high arc welding temperature. The flux’s inert gas and slag “encapsulate” the weld and keep the gases in the air away.
AC Vs. DC Currents
DC provides current that flows in one direction, and AC alternates the direction of current flow multiple times a second. For example, a 60 Hz AC supply would alternate the flow direction 120 times a second.
The current differences are important. For example, with DC, magnetic fields can form, induced by the consistent flow of electric current in one direction.
Magnetic fields can move the arc so that it does not travel the shortest gap between the electrode and metal. This can cause spatter, porosity, and incomplete fusion and often happens at inside corners or at the end of welds. This is called arc blow.
So, it’s an issue with DC. But AC oscillates the current, and the magnetic fields are constantly being disrupted and never organize enough for arc blow to be an issue.
Also, DC welders are a bit more expensive to purchase. So, arc blow and initial costs are the two main cons for DC. You may even say just use AC arc welders. But for certain processes, like MIG welding, DC’s advantages far outweigh these disadvantages.
DC arc welders offer a smooth, easy-to-control arc, and they work better on thin materials. You also get less spatter, and in general, DC beads are “prettier.” For these reasons, you see DC is often used in arc welders, and many users prefer it over AC.
AC arc welders are often inexpensive and do not allow magnetic fields to be set up. So, it can be used in situations prone to arc blow. AC welders also penetrate well and are used in places like shipyards that regularly deal with thick pieces.
Another benefit of AC, it handles metals with problematic oxide layers on the surface, like aluminum. As the current oscillates, it efficiently removes the oxide layer that can interfere with and inhibit the fusion of the metal pieces.
What Is Arc Welding Used For?
The most common and simplest form of welding is arc welding. So, it is found in use across all industry sectors, such as automotive, aerospace, oil and gas, manufacturing, power, construction, and many more.
Applications include vessels, pressurized vessels, pipes, tanks, ships, bridges, railroads, automobiles, farm equipment, metal art sculpture, trailers, etc.
In short, due to its quick and economic nature when joining metal, arc welding is used for just about any time two pieces of metal need to be joined. But the high heat generated can be a problem for some jobs. So, arc welding is not for every project.
For these applications, our capacitor series below are specially designed to work with arc welders.
Advantages & Disadvantages Of Arc Welding
Like all things in life, arc welding has its strong points and drawbacks. These are summarized below:
· Good impact strength
· High production rates (lowers the cost per unit of weld)
· Strong, seamless welds with no air gaps
· Easy to learn and use
· Portable equipment, easy to store
· Versatile, works on many types of metal
· High-quality, strong welds
· Accessible (No license or special training needed)
· Toxic fumes need ventilation or respirators
· More waste than with other processes
· Requires practice to achieve a high skill level
· Burn through on thin materials