What is Arc Welding?
Arc welding is a welding process used to join metal to metal by using electricity to generate enough heat to melt metal and the melted metals, when cooled, result in a joint of the metals. It is a type of welding that uses a welding power supply to create an 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 current (DC) or alternating current (AC) and consumable or non-consumable electrodes.
The welding area is usually protected by some type of shielding gas, vapor, or slag. Arc welding processes can be manual, semi-automatic, or fully automatic. Arc welding was developed in the late 19th century and gained commercial importance in shipbuilding during World War II. Today it remains an important process for the manufacture of steel structures and vehicles.
How Does Arc welding Work?
Arc welding uses an electric arc to melt the work material. First, a ground wire is attached to the material. Next, the welder places an electrode lead against the work material.
When the welder pulls the electrode away from the material, it creates an arc, also known as a continuous plasma discharge, due to the electrical breakdown of gas. Arc welders use either alternating current or direct current and are used to create a very concentrated, narrow spot weld.
Arc welding is a fusion welding process used to join metals. An electric arc from an AC or DC power source creates intense heat of about 6500°F, which melts the metal at the joint between two workpieces.
The arc can either be guided manually or by a machine along the joining line, while the electrode either only carries the current or conducts the current and at the same time melts into the weld pool in order to feed filler material to the joint.
Since the metals react chemically with oxygen and nitrogen in the air when they are heated by the arc too high temperatures, a protective gas or slag is used to minimize contact of the molten metal with the air. After cooling, the molten metals solidify to form a metallurgical bond.
DC vs. AC Currents
The electric power supply for arc welding can come from either a direct (DC) or alternating (AC) current.
Direct current (DC) arc welding is often used in stick welding and lower-voltage cases and is generally preferred over AC. This is because the DC current uses electrons that flow steadily in one direction, creating a smoother and more stable arc.
Alternating current (AC) arc welding has greater volatility in the electrons, as they change direction constantly.
AC current is usually a secondary choice in welding but can be helpful in some instances, like when a stronger current is needed to prevent the arc from blowing out or for transmitting electricity over large distances.
Types of arc welding
The different types of arc welding are roughly divided into the non-consumable electrode and consumable electrode types, as well as the arc generation and welding principles.
Consumable vs. Non-Consumable Arc Welding
The electrodes (or “sticks” or “rods”) used in arc welding can be either consumable or non-consumable.
A consumable electrode not only conducts the current but also supplies filler metal to the joint. This means the electrode is made of a type of metal that melts along with the metals being welded together. This type of welding is often used in the manufacture of steel products.
A non-consumable electrode, on the other hand, is made of material that is not melted during the weld, such as tungsten, which has an extremely high melting point.
Arc Welding can be categorized into two different types;
|Electrode consumption||Welding method|
|Non-consumable (non-fusible) electrode type||1. TIG welding |
2. Plasma welding
|Consumable (fusible) electrode type||1. Shielded metal arc welding |
2. MAG welding
3. MIG welding
4. Electrogas arc welding (EGW)
Different Types of Arc Welding Process
There are different types of arc welding. Which arc welding method you use depends mostly on the metal. Following is an overview of various kinds of arc welding techniques:
1. Flux-cored arc welding (FCAW)
This type of arc welding uses tubular electrodes filled with flux. While emissive flux shields the arc from the air, none missive fluxes may need shielding gases.
It is ideal for welding dense sections that are an inch or thicker because FCAW has a higher weld-metal deposition rate.
2. Gas metal arc welding (GMAW)
GMAW or MIG welding shields the arc with a gas like argon or helium or a gas mix. The electrodes have deoxidizers that prevent oxidation, so you can weld multiple layers.
This method has several benefits: simple, versatile, economical, low temperatures, and easily automated. This is a popular welding technique for thin sheets and sections.
3. Gas tungsten arc welding (GTAW)
GTAW or TIG welding is often considered to be the most difficult. Tungsten electrodes create the arc. Inert gases like argon or helium or a mix of the two are used to protect the shield.
Filler wires add molten material if needed. This method is much “cleaner” as it doesn’t produce slag, making it ideal for welding jobs where appearance matters as well as thin materials.
4. Plasma arc welding (PAW)
This arc welding technique uses ionized gases and electrodes that create hot plasma jets aimed at the welding area.
As the jets are extremely hot, this method is for narrow and deep welds. Plasma arc welding (PAW) is also good for increasing welding speeds.
5. Shielded metal arc welding (SMAW)
SMAW is one of the simplest, oldest, and most adaptable arc welding methods, making it very popular. The arc is generated when the coated electrode tip touches the welding area and is then withdrawn to maintain the arc.
The heat melts the tip, coating, and metal so that the weld is formed once that alloy solidifies. This technique is typically used in pipeline work, shipbuilding, and construction.
6. Submerged arc welding (SAW)
SAW works with a granular flux that creates a thick layer during welding, which completely covers the molten metal and prevents sparks and spatters.
This method enables deeper heat penetration because it acts as a thermal insulator. SAW is sued for high-speed sheet or plate steel welding. It can be semiautomatic or automatic. However, it is limited to horizontal welds.
7. Electro-Slag Welding (ESW)
A vertical process is used to weld thick plates (above 25mm) in a single pass. ESW relies on an electric arc to start before a flux addition extinguishes the arc. The flux melts as the wire consumable is fed into the molten pool, which creates a molten slag on top of the pool.
Heat for melting the wire and plate edges is generated through the molten slag’s resistance to the passage of the electric current. Two water-cooled copper shoes follow the process progression and prevent any molten slag from running off.
Where Is Arc Welding Used?
Arc welding is commonly used to join materials and is used across a lot of different industries.
The aerospace industry uses arc welding to manufacture and repair aircraft, join sheeting, and for precision work. The automotive industry uses arc welding to bond exhaust systems and hydraulic lines. Arc welding can deliver extremely strong bonds even between thin metals.
The construction industry uses arc welding to guarantee strong, sustainable connections within buildings, bridges, and other infrastructures. Other industries that use arc welding are the oil and gas industry and the power industry.
The arc process uses a variety of rods that have different strengths, weaknesses, and uses which can impact weld quality. The rod is connected to the welding machine and a current is passed through to join workpieces together.
In some cases, such as with SMAW, the rods melt to become part of the weld – these are consumable electrodes. In other instances, such as with TIG, the rods do not melt – these are non-consumable electrodes.
Rods are generally coated, although the exact type of coating varies. While uncoated rods are available, these are far less common, create more spatter, and can make it difficult to control the arc.
Coated rods are better to reduce or eliminate contaminating oxides or Sulphur. The three types of coating include cellulose, minerals. or a combination of the two.
Whether coated or uncoated, the correct rod needs to be selected to create clean, strong welds with the right bead quality.
Application of arc welding
The applications of Arc Welding include the following.
- Used in the welding’s of sheet metals
- For welding thin, ferrous & non-ferrous metals
- Used to design pressure & pressure vessels
- The developments of piping in industries
- Used in the domains of automotive and home furnishing
- Industries of Shipbuilding
- Used in the manufacturer of aircraft & aerospace, Auto body restorations, Railroads.
- Industries like construction, automotive, mechanical, etc.
- Gas Tungsten Arc Welding is used in aerospace industries to connect many areas like sheet metals.
- These welding are used for repairing dies, tools, and mostly on metals that are made with magnesium & aluminum.
- Most of the fabrication industries use GTAW to weld thin workpieces, particularly nonferrous metals.
- GTAW welding’s are used where extreme resistance to corrosion as well as cracking over a long period of qualities are required.
- It is used in space vehicles manufacturing.
- Used to weld small-diameter parts, thin wall tubing, making it applicable in bicycle industries.
Advantages of arc welding
There are a number of advantages to using arc welding compared with many other formats:
- It is suitable for high-speed welds.
- It is a simple welding apparatus.
- It can work on AC or DC.
- Superior temperatures.
- Less smoke or sparks are involved.
- Portability as a result of the simple equipment.
- It is a fast-welding process when compared to others,
- It offers strong joints.
- Produces very little distortion.
- High corrosion resistance.
- It has the ability to weld on porous and dirty metal.
- It is the equipment that is inexpensive.
- Its operation can be performed during wind or rain.
- Its power supply can be used where there is electricity and the alternative can use be if there is no electricity but generators.
- Smooth welding is achieved.
- It is a good impact strength.
- Arc welding beads can be used to create designed on fine metals.
- It can be carried out in any atmosphere.
Disadvantages of arc welding
There are a few reasons why some people look to other options beyond arc welding for certain kinds of projects. These downsides can include:
- Require skilled welders.
- Cannot be used for reactive metals like AI or Ti.
- Not suitable for welding thin metals.
- Not all thin metal can weld on arc welding.
- A well trained and skillful operator is needed for the task.
- Increases of project costs as wastage is inevitable during the process.