If you have any interest in welding or a welder, you have heard about the AC and DC terms. AC and DC are current types utilized during the welding procedure. Welding requires a constant current flow with varying polarity based on the welded material. To ensure you have an excellent weld, it is essential you know what AC and DC currents mean.
What is AC Welding?
AC welding is an alternating current where electrons flow to change directions frequently. In one second, the current switches its polarity over 120 times. Polarity is the electrical circuit produced after switching on the welder with positive and negative poles. AC welding aids to transfer power for extended distances.
This type of current is not commonly used and operates where no DC machines exist. However, there are areas where the current is most preferred. AC welding is ideal where there is no other electricity supply. The current is suitable for fast fills, down-hand heavy plate welds, and aluminum TIG welding. It is also used in magnetized metals since DC welding is not applicable. AC welding offers higher current intensity that enables the weld to penetrate deep. This makes it ideal for machinery repair and fixing arc blow problems.
Types of AC Welding
The type of AC welding method to apply mainly depends on the metal you want to weld. There are various types of AC welding, as discussed below:
- Gas Metal AC Welding (GMAW or MIG welding) – The welding allows the formation of an electric arc between the welded material and a usable wire electrode. The shielding gas helps to safeguard against impurities, while the welding gun supplies the electrodes. Consequently, the workpiece material dissolves and sticks together. The method is simple, economical, versatile, and easily automated. It is used to make thin sections and sheets.
- Shielded Metal Arc Welding (Stick Welding) is one of the easiest but oldest AC welding types. The electric arc is formed when the coated electrode tip meets the workpiece material. It is then removed for arc maintenance. The heat then dissolves the coating, tip, and metal, and the weld is created after cooling. This type of AC welding is used in construction, shipbuilding, and pipeline work.
- Gas Tungsten Arc Welding (GTAW or TIG Welding) – to form a plasma arc, this welding method uses the non-usable tungsten electrode, an inert shielding gas, and continuous power flow. The technique does not generate any slag since it is cleaner. Gas tungsten arc welding is suitable for welding thin materials such as non-ferrous metals and stainless steel.
- Submerged Arc Welding (SAW) – the electric arc is formed under the flux powder’s bed, which offers alloying components, slag, and shielding gases for the melted pool. SAW method allows heat to penetrate deep as it functions as a thermal insulator. It is either automatic or semi-automatic. This technique is ideal for plate sheet welding.
- Plasma Arc Welding (PAW) – this type of arc welding utilizes electrodes and ionized gases to form a plasma arc at the welding surface. It is used in both deep and narrow welds. The method is also suitable for raising welding rates.
Advantages of AC Welding
- The AC equipment is less expensive compared to DC welding machines.
- It is suitable for aluminum welding.
- The AC welding helps to fix arc blow problems.
- It is used when there is no other power supply available.
Disadvantages of AC Welding
- The quality of welding is lower than the DC welding.
- It creates more spatter
- The method is less dependable and hard to handle
Applications of AC Welding
The method is ideal for welding over two magnetic metals. Here are some of the AC welding applications:
- Shipbuilding where plate metals need to be penetrated deeper
- When welding magnetized materials
- Fast fill
- TIG welding aluminum at high temperatures is required.
What is DC Welding?
DC (direct current) welding is a type of electric current where electrons flow in one direction. The current is known to have a constant polarity, either negative or positive. DC is commonly used in devices with low voltages like remote controls and smartphone batteries.
In welding applications, the DC polarity helps to develop a high-quality (smoother) welding output than the AC. DC welding forms a very stable arc with more minor spatter. When you want to have a deeper steel penetration, use the DC positive, while it is advisable to utilize the DC negative when you want quicker deposition speeds.
DC welding is ideal where the AC welding cannot be applied. Such areas include stainless steel TIG welding, single carbon brazing, and vertical welding. The method is perfect for users who want a remarkable increase in massive deposits. This is because despite AC welding having a significant penetration, it does not have a large deposition rate; hence not ideal. The DC welding works better with various metals. However, it does not work best with aluminum as it needs high heat intensity.
Advantages of DC Welding
- The electric current develops more smother welds since constant polarity and electrons flow in a single direction.
- DC welding uses less expensive and easy to operate machinery.
- It ensures that the arc is stable and steady, making it reliable and easier to handle than AC welding.
- DC welding is more suitable for thinner metals than AC.
Disadvantages of DC Welding
- DC welding encourages arc blow.
- Since DC is not provided with electrical grids, they require an internal transformer to convert the current for consumption. This makes the technique more costly to work with.
- The DC welding cannot be used to weld aluminum as it does not generate the high heat intensity needed for this process.
DC Welding Applications
DC welding has a wide variety of applications, as highlighted below:
- The method is commonly used in stick welding.
- Single carbon brazing
- Stainless steel TIG welding
- Welding thin metals
- Vertical and overhead welding
- Hard facing
- Cutting tap
- The build-up of massive deposits
Significant Differences between AC and DC Welding
- Size – the DC welding machinery is more significant than the AC weld machines.
- Arc blow – it is challenging to handle the DC welding machinery compared to the AC welding machine.
- Weight – DC machinery are heavier than the AC welding machines
- Voltage – the DC machinery has a higher voltage drop; hence used at short distances, while AC welding machines have a lower drop in voltage, making them ideal for further use.
- Price – DC machinery is expensive compared to AC welding machines.
By now, you have a better understanding of what AC and DC welding entails. That is, their uses/applications, pros and cons. To attain better penetration and excellent welding outcomes, use the proper polarity and current with the provided electrodes. When you use improper polarity and current, you end up getting poor penetration, overheating, excessive splatter, no arc control, irregular bead shapes, and fast electrode burning.
Therefore, it is highly advisable to know the type of piecework you want to use and the conditions necessary for your task. This helps you to determine if you will use either AC or DC welding. It is essential to follow all the safety procedures when you use a welding machine. Wear fire-resistant shoes, gloves, clothing, and a welding helmet.