Arc Welding : Definition, Basics and its various types

I hope you are very much aware with the term i.e. Welding. We have seen the overview of a welding process and we have also seen some essential welding tools and resources in our previous posts i.e. Important welding tools and equipment and their uses. 

Let us get more in depth and understand each term associated with welding practices. So, let's start with the Arc welding process here with the help of this post. 

Arc welding process

In the arc welding process, the welding temperature is produced by an electric arc, established

between an electrode and the metal being welded. The temperature of the arc is 7000 degrees Celsius. 

Following figure indicates the arc welding set-up. 

The welding set-up uses either AC or DC transformer for striking the arc between the electrode

and the workpiece. If one terminal is connected to the electrode and the other to the end of the

workpiece, then the circuit is completed through an air gap between the electrode and the workpiece.

An air gap generally ranges from 3 mm to 6 mm. The proper gap should be maintained for

the good result.

Types of Arc Welding

The commonly used arc welding processes are as mentioned here 

1. Carbon arc welding 

2. Metal arc welding 

3. Submerged arc welding 

4. Inert gas welding (TIG and MIG)

5. Plasma arc welding 

6. Electro slag welding

Carbon arc welding

In the carbon arc welding process, the arc is obtained between the carbon electrode and the workpiece or between two carbon electrodes. This welding is suitable for welding of steel sheets, copper, alloys, etc.

Metal arc welding

This is also called shielded metal arc welding (SMAW). The metal arc welding set-up is shown in the following Figure.

Heat required for the welding is obtained from the arc spark between the coated electrode and the workpiece. 

The material droplets are transferred from the electrode to the workpiece through

the arc and deposit along the joint to be welded. 

Submerged arc welding

The setup for submerged arc welding is shown in the following figure. This process is so named because the metal arc is shielded by a blanket of flux. 

In this process, instead of a flux-covered electrode, granular flux and a bare electrode is used. Flux is deposited continuously in front of the electrode and the flux feeder and the electrode feeder together move as the welding proceeds. 

The flux is filled in sufficient depth to submerge completely the arc column so that there is no smoke or splatter and the weld is shielded from the effect of all atmospheric gasses. 

Inert gas welding

In conventional arc welding, the fluxes are used to shield the atmosphere around the molten metal. But in inert gas welding, inert gasses such as argon, helium, carbon dioxide are used for surrounding the electric arc and thus keeping the atmospheric air and other contaminants away from the molten metal pool. 

The following two methods are employed in inert gas welding 

• Tungsten Inert Gas welding (TIG)
• Metal Inert Gas welding (MIG)

Tungsten-inert gas welding (TIG) 

It uses a non-consumable tungsten electrode mounted at the center of the torch as displayed here in the figure.

The inert gas is supplied to the welding zone through the angular path surrounding the tungsten electrode.  

Welding operation is done by striking the arc between the workpiece and the tungsten electrode in the atmosphere of inert gas. 

Metal-inert gas welding (MIG)

The metal-inert gas welding set-up is shown in the following figure. In this process, the tungsten electrode is replaced with a consumable electrode. 

The electrode is continuously fed to the arc at the rate at which it is consumed and transferred to the base metal. Arc is shielded by an inert gas, which flows from the nozzle through which the electrode also passes. 

Plasma arc welding

The plasma arc welding, as displayed in the figure, is an electric arc welding process which employs a high temperature arc or plasma jet to obtain the melting and join of metals. 

In this process, a gas (argon or hydrogen) is passed through an electric arc, where the gas gets ionized. This process uses two inert gasses, one forms the plasma and the second shields the arc plasma.

Electro slag welding

The electro slag welding set-up is shown in the following figure. 

In electro slag welding, the workpieces to be welded are positioned vertically with the necessary gap between them. The copper shoes (water cooled) slides on either side of the gap form a well in which flux is deposited. 

The electric arc is struck between the electrode and the joint bottom with the help of a piece of steel wool. The arc melts electrodes and flux that forms the molten slag. The heated metal collects in the pool beneath, the slag slowly solidifies thereby forming the weld head joint of the two workpieces.

We will see another topic i.e. Gas Welding in our next post.

Reference 

Engineering Practices by Mr. S. SUYAMBAZHAHAN