AC Vs DC Welding

March 2, 2021

To those out there that aren’t privileged enough to hold fancy welding certifications and qualifications, understanding the difference between DC and AC welding can prove tricky.

The AC vs. DC welding thing can sometimes be a little misleading, so you must pit the two face-to-face when comparing them.

So what makes alternating current (AC) and direct current (DC) so different? Their polarity is where their differences lie. Direct Current welding is direct current straight polarity-based.

On the other hand, alternate current welding quickly alternates between DC positive and DC negative.

Although most welders prefer to use DC welding on most of their tasks, AC can come in handy in certain specialized scenarios.

These applications include when dealing with arc blows, TIG welding aluminum, and welding in places with electrical outlets that only give you 110-volts.

Alternating current is also more commonly used by beginner welders. On the other hand, DC welding is ideally used in heavier applications.

The welds don’t spatter much and come out smooth and way stronger.

DC welding needs internal electrical components to get straight polarity out of alternating polarity.

This adds to both the cost and size of the machine. They also normally need a current of around 220V, meaning you’ll need special wiring wherever you’re working from.

What’s AC Welding?

What’s AC Welding?

An alternating current is an electric current you’ll find in AC welding.

Unlike direct current welding, alternate current welding uses an electric current the alternates quickly between negative and positive.

Instead of a straight line current, picture fluctuating currents on a graph.

Alternating current is what’s standardly used in all home wiring, which means home welders won’t need to modify the wiring to pass the current.

Advantages of AC Welding

Advantages of AC Welding

Although AC welding has its fair share of disadvantages, especially because it creates such a messy result, it also has plenty of pros.

You can use AC welding in many different ways that are practical for repair and easy-to-use in industrial settings.

One of AC welding’s biggest pros is that you can use it with metals that have magnetic fields. Sometimes the arc will dis-align with the electrode.

It’s normally following the magnetic current in the metal being welded. This is known as ‘arc wandering.’ It can make it tough to get straight, clean welds.

There’s a lot of arc wandering in DC welding. With AC, there’s none. This comes in handy when you’re repairing heavy machinery (which has a magnetic field).

Logging equipment, construction machinery, and such things as forklifts are good applications.

Alternating current buzz box welders are typically used as second options when you don’t have access to 220V current.

However, it’s a great way to weld when power is in short supply, like in a small garage or home shop.

The high spatter shouldn’t discourage you. You can expect this with AC wielding. It’s a completely normal reaction.

TIG welding aluminum also favors alternating current. Thin layers of aluminum oxide coat the aluminum, interfering with the weld bead.

The alternating current’s quick polarity jumps have a scrubbing effect that breaks these layers up and keeps the risk of contamination low.

Although direct current welding is generally a bit better for most industrial applications, alternating current welding is ideal for those that don’t have 220V outlets.

While you can modify your small space or home to have 220V outlets, you need to hire an electrician to help you do this.

This makes it perfect for welding at home, fixing small automotive parts and appliances, as well as fabricating anything that needs a little sprucing up.

Disadvantages Of AC Welding

Disadvantages Of AC Welding

Not many kinds of welding prefer alternating current polarity. DC welding usually provides the best results in most welding jobs.

One of the biggest disadvantages it has is arc wandering. A lot of the time, you tend to lose the arc in AC welding.

Because it has a current that fluctuates back-and-forth, its arc always needs to refresh itself every time it turns the current between negative and positive.

This can sometimes cause the welder problems because it helps lead to breaks in the weld, in turn, making it weaker.

This is an issue many beginner welders will struggle with. It can be tough to consistently try and keep the weld going and crack an arc.

Everything is made harder when you’re to use a tool that drops the arc.

Another common problem is spatter, small pieces of metal debris typically found around AC welds. This is also because of the fluctuating currents.

Most kinds of welding will produce spatter; however, it’s much worse with AC. You’ll spend more time cleaning off spatter with this kind of polarity.

What’s DC Welding?

What’s DC Welding?

A direct current is used in DC welding to supply electricity to the electrode that’s used for welding the two different metals together.

You know all the wavy lines you picture when thinking about a graph? Well, this kind of welding doesn’t look like that. It looks like steady, straight streams on a graph.

This stability helps prevent the arc from constantly stopping every time there’s a polarity change.

Direct current has the ability to use both electrode-negative or electrode-positive polarity.

Negative polarity has a current flow that goes to the electrode, from the welder, to what’s being welded and then back again to the welder.

Positive polarity, on the other hand, has a current flow that goes to the workpiece, after it has left the welder, to the electrode and the back again to the welder.

Electrode-negative polarity is also commonly known as ‘straight’ polarity. It’s what people prefer to use on their welding jobs.

Straight polarity will produce a faster electrode melting and a hotter arc. This allows you to be more productive and gives you a chance to lay down beads faster.

Unless something requires special attention, straight polarity direct current is almost always the best bet.

Reverse or electrode-positive polarity produces deeper penetration. It’s ideal for the welding of thick materials.

The process isn’t as fast as straight polarity; however, it’s at its best when it comes to welding thick materials.

Although, you’ll have to work a bit slower when using reverse polarity. But that’ll prove to be an advantage when your working with materials that are half an inch thick.

Advantages Of DC Welding

Advantages Of DC Welding

Despite all the drawbacks of DC welding, there are also many times it’s better than using AC welding.

In situations where you’re looking for but don’t necessarily need an aesthetically-pleasing, smooth weld, DC welding might just be your best bet because of its non-changing, steady polarity and welds that have minimal spatter.

Maybe the best time to use DC welding techniques is when the welds will be seen and where they need to look visually appealing.

Common instances include tools, vehicles, and furniture. DC welding is also perfect when you want to make or fix parts that need to withstand extreme abuse or pressure.

DC welding can be applied to include large fuel tanks, gussets, chassis, tow hitches, and cross members.

These kinds of applications need the welds to both to look clean and be able to stay strong for long periods.

Disadvantages Of DC Welding

Disadvantages Of DC Welding

Even though DC welding produces better welds overall, it has a few disadvantages that make it tougher to use in day-to-day applications.

In some instances, these disadvantages make it harder to use direct current welding in places where it’s ideal. That said, its biggest con is its cost.

DC welding requires a current that’s not found in most standard electrical grids. This means that you’ll probably need to install an internal transformer so that you can convert the AC currents to DC.

These transformers add both complexity and weight to DC welders, making them pricier. DC tools also need 220V circuits to work, meaning you’ll need the assistance of an electrician at some point.

Hiring an electrician can sometimes cost the same as getting the welder itself.

DC welding also has arc blow issues. The magnetic currents that flow inside the weld metals will help dis-align the arc with the electrode, which eventually will lead to a ruined bead.

Because arc blow is so problematic in DC welding, most welders opt to go the AC welding route when handling most jobs.

AC welders don’t have such a big arc blow problem because the polarity of the arc flips too quickly.

In general, you’ll experience fewer problems when DC welding compared to AC welding.

However, DC welding needs more resources and operator skills. Even though it’ll cost more to use DC welding, most professionals would rather use this current.

If you intend on taking welding seriously, or if you’re looking to use TIG or MIG, your best bet would be to go the direct current route.

AC Welding Machines

AC Welding Machines

Current is not the only difference DC, and AC welding has. AC-only welders can only typically use arc welding techniques.

On the other hand, DC machines can be used for TIG, MIG, and arc welding. If you can’t decide which one to use, you can get welders that can go both ways.

Although, this will mean you’ll have to cough up a little more for this feature. AC welders are often more compact and a bit smaller.

They’re also usually way more affordable than their DC welder counterparts and are more portable as well.

Being so light means they can be easily transported in and out of work sites for machinery and building repair purposes.

In addition to being affordable and convenient, AC welder machines are also easy to use.

The AC machine’s arc blow ranges from easy to control to non-existent. The machines also use 110V outlets.

DC Welding Machines

What’s DC Welding?

DC welder machines are the brutes when it comes to size. Heavy, large, and hard to move, these machines are sturdier but clunkier than the AC counterparts.

Their size makes them perfect for industrial and heavy-duty applications beyond fixing household metal casualties and the occasional car part.

DC welding machines, unfortunately, are quite spendy. This is why most beginners will choose AC machines over DC ones.

However, welding businesses and professionals with huge workloads will be better off with bigger units. DC welding machines are ideal for warehouse settings, i.e., where 220V currents can be made available.

How To Know Which Current To Use?

How To Know Which Current To Use?

When picking the type of welder you want, it can be hard sifting through all the options available to you.

There are many people and ads out there that’ll tell you what to get.

If you’ve already got a welder or already got both a DC and AC machine, you might not know which one you’ll need to use for certain applications and projects.

If you’re going to be welding at unusual angles or overhead, you might want to use DC welding because it has less spatter.

On the other hand, AC welding is ideal for small home applications. You won’t have to modify the electrical grid to use AC welders in your home.

If you’re just starting, you should strongly consider going to the AC route.

Wrapping Up

There are several different kinds of welder machines out there, each with unique specs that need specific currents and materials.

The most important difference is between direct current and alternating current welders. Understanding the difference between the two is important when figuring which one best suits you.

Small AC welders require only 110V outlets, while the bigger welder machines will need 220V outlets. Most shops and home garages usually do not have 220V outlets.

You need to keep that in mind if you’re considering a DC welder.

All in all, if you’re just starting with welding, then you should consider using alternating current welders. They’re more convenient and cheaper to own.

However, if you are looking for something more professional and hefty, then what you’ll need is a DC welder machine.

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