ac vs dc Welding

AC vs DC Welding – Learn Which One Is The Best & Why?

What first comes to mind when you hear or read the term AC/DC. For some, it gets them thinking of a certain Australian rock band. But what does it mean for welders? In particular in regards to arc welding.

Arc welding involves the use of a power supply to create an arc between an electrode and the material being welded. To get the perfect weld you need to use the right power supply, which can either be Alternating Current (AC) or Direct Current (DC).  

ac vs dc Welding

This brings us to the question of which is stable between ac vs dc welding. Both ac and dc welding have their pros and cons. But generally, DC is used in the welding of ferrous metals while AC is used in the welding of non-ferrous metals.

Now let’s take a closer look at the topic of ac vs dc arc welding by analyzing what each type of welding is good for.

ac vs dc welding process

AC Welding

What is ac welding?

To understand the difference between ac and dc welding it is important to look at each type separately. That being said, what exactly is AC welding. Now firstly, it is important to note that AC welding does not denote a specific type or technique of welding.

Rather it refers to how electric currents flow from a power supply to a welding machine. In AC the flow of current is not in one direction, but rather constantly changes back and forth. In AC the polarity of the current can change up to 120 times per second.

When the polarity changes from negative to positive the output for a split second is 0. This means that for a split second the welding arc is extinguished. It is for this reason that there are electrodes specifically designed for AC welding.

AC Polarity Output

Welding processes that use AC

Due to the unique nature of AC welding, it is best suited to TIG aluminum welding. Aluminum is a unique metal that has a tenacious oxide film on its surface. When the AC switches to positive it helps clean the surface and remove the oxide film.

Also, AC supports welding at higher temperatures. Most types of welding techniques use DC. However, TIG aluminum machines use AC. It is also possible to get a machine that uses both AC and DC.

These are usually multi-process machines that can be used for MIG or stick and TIG aluminum welding. 

AC welding applications

The first application of AC welding is in the welding of aluminum and other non-ferrous metals. AC typically achieves a deeper penetration and thus is preferred in the shipbuilding industry. Another great application of AC welding is in the welding of magnetized metals.

Advantages of AC welding

  • Can be used on magnetized metals or fields
  • Is suited to welding non-ferrous metals such as aluminum and magnesium
  • Achieves a deeper weld penetration
  • Can be used for high-temperature welding

Disadvantages of AC welding

  • Produces more spatter
  • The arc is more difficult to handle compared to DC

DC welding

What is DC welding?

In DC the electric current flows in one direction. Thus there is constant polarity which can either be positive or negative. This type of current is used in low voltage devices such as phones, remote controls, and others.

In welding, DC tends to be faster and results in quicker electrode melt off. As already mentioned the polarity can either be positive or negative. Also referred to as straight, negative electrode polarity is faster than positive electrode polarity.

However, the negative polarity produces less heat than the positive electrode. This makes negative electrodes ideal for welding thinner metals.

dc polarity output

Types of welding processes that use DC

DC is more widely used than AC. This means almost all welding processes rely on DC. Stick welding and MIG welding are the main welding processes that utilize DC.

DC welding applications

DC welding is often used in stick welding applications. This means you will find it being used in welding applications that require either overhead or vertical welding. Also, since AC is not suited for welding thinner metals, DC is used instead.

While AC is used in TIG welding application in particular in the welding of aluminum, DC is used in the TIG welding of stainless steel. DC is also used in single brazing of carbon.

Advantages of DC welding

  • It produces a smoother weld and there is very little spatter
  • Maintains a constant stable arc meaning it is easier to handle compared to AC
  • Due to it being easier to handle machines that use DC are easy to use
  • For welding thinner metals it is better than AC
  • Unlike AC it is used in a wider variety of welding processes

Disadvantages of DC welding

  • Does not work well for high-intensity heat
  • Relatively more expensive compared to AC based machines

The main differences between AC and DC

AC vs DC Welding - Learn Which One Is The Best & Why? 1
Effects of AC DC Welding Process

Machines that use these two current types differ greatly. For starters, AC based machines tend to be lighter than their DC-based counterpart. Moreover, AC machines are also cheaper. Thus, when it comes to weight and price AC machines edge out their counterparts.

However, do not rule out DC machines just yet. What they lack in portability and affordability they more than makeup for in versatility. Whereas AC machines are best suited to TIG aluminum welding DC machines can do virtually anything.

DC machines can be used for stick, TIG, and MIG welding. Also, these machines can be used to weld a wider variety of metals including heavy aluminum. Thus, while the cost of AC machines is appealing the quality of the weld is not.

Which One Is Better AC OR DC

When you think about it, they both have their perks. And it all comes down to your welding needs. Nevertheless, in regards to quality and versatility, DC is king. This is the reason why most high-end welders are DC-based.

Where AC edges out DC is in TIG aluminum welding. So which is better ac welding vs dc welding? Well, for aluminum AC but stainless steel and other ferrous metals DC.

Conclusion

There is a lot to be said about AC and DC-based welding machines. But the bottom line is that it all comes down to several things. Number one is what you are welding. For ferrous metals and magnetized metals, AC is better.

DC excels in the welding of ferrous metals. Thus while DC is more versatile, there is still a place of AC based welders in the market. 



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