DC Vs AC Welding
People talk about dc vs ac welding because some believe that DC welding is better than AC welding while others say otherwise. Yet, many of us don’t clearly understand the differences between these two. So here we will discuss what is all about DC welding, AC welding and what it can contribute to our tasks as welders. We shall also talk about their advantages over the other to give you a head start which to use when using different arc welders or when working on certain types of metals.
First, let’s talk about what is DC (Direct Current) and AC (Alternating Current) before we go towards ac vs dc welding. Why we call DC a direct current is because the flow of electricity or the movement of the electrons along the path in an electrical system is in one direction. DC is utilized by small devices like laptops, cellphones, or any electronic devices that require electricity in small constant current. So the current you use on your gadgets is DC which can also derive its power from AC and store this power into the batteries like the rechargeable batteries.
Why we call AC as the alternating current is because its flow of electrons is in alternate or reverse direction like half the time in one direction and the other direction for the same time. So AC changes its polarity 120 times/second on 60-hertz current. In our homes and offices, we use the DC which our large appliances need. So for most of you to better remember, AC is for large appliances and the usual power sources for homes and buildings and DC is for gadgets with batteries.
AC Vs DC Welding
In welding, there is what we call the AC and DC polarities which means if you use the AC polarity in welding, this is called AC welding and if DC polarity is used this becomes the DC welding. So an AC/DC welder can be just one single unit though there are also single polarity units but are not very common these days. With the dual-polarity welders, you can now easily shift the polarities of your arc welder to match the type of electrodes you want to use thanks to the internal transformers that the new arc welders are loaded with.
Nevertheless, we could see AC and DC terminals on many types of arc welders because there are electrodes that can be effective only on AC mode. AC has no specific polarity because it changes its polarities fast as the electrons can move back and forth like vibrating currents. Polarity greatly matters in welding because you could manipulate the flow of current based on the type of electrodes you are using and the metal you are welding. By choosing the right polarity, you could produce a stronger bond, control the spatters, reduce the heat, and so on.
This goes also to say that if you will be using the wrong polarity you could damage certain metals especially those that are prone to oxidation. So what we are concerned about ac vs dc welding is also how and when to choose the right polarity and how polarity could help improve your work?
AC DC Welding - How Polarity Affects
To explain polarity further and to quantify ac dc welding, every electrical unit has a negative and positive pole in its electrical circuitry. Most arc welders machines are based on the constant DC polarity so we may see on our arc welding machines written signs like “DC straight polarity” or DCEN and “DC reverse polarity” or DCEP.
Accordingly, the advantage of each is that in arc welding, DCSP can provide a faster melt-off and faster deposition rate of the electrode while DCRP can produce a deeper penetration of the molten weld. However, it may not always work this way because your use of polarity will also depend on your use of electrode types. For example, the high cellulose covered mild-steel rod for stick welding can only work on positive polarity while the other rod types will work either for negative or positive polarity. Nonetheless, stick welding generally requires DC as this type of current can create a smoother and better stable arc with less spatter.
On the other hand, you can also use AC on stick welding but expect that there would be a lot of spatters and arc outages. So stick welding on AC is only advisable for beginners just to feel the method of this welding application.
DC Vs AC Welding
As we further discuss dc vs ac welding, in welding, there are three popular types of arc welding applications – MIG (Metal Inert Gas) welding, TIG (Tungsten Inert Gas) welding, and the SMAW (Shielded Metal Arc Welding) or also called stick welding. These welding methods all require electric current to produce arcs that’s why their methods arc collectively called “arc welding”. Now, most of these machines can either use AC or DC polarities so they are highly capable of DC and AC welding.
Most MIG welders that require gas shielding use DC. Remember that DC is tamer than AC. So why AC on MIG welding? Because other than the spark that the electrode produces which melts itself, the shielding gas also adds to the heat. So a combination of the spark and the heat from the arc are enough to melt the wire electrode. But if you switch to gasless MIG welding or flux-cored welding, you must switch to AC because there is no shielding gas involved like carbon dioxide or argon. The only role of the flux on the electrode when it burns is to act as a shield to the weld puddle.
TIG welders today can operate both on AC and DC because they are equipped with inverter systems. An inverter is a device capable of converting DC into AC electricity regardless of the voltage being used. In stick welding, the welding process can both work on reversed polarity (electrode-positive) for deeper penetration and straight polarity (electrode-positive) for a faster deposition rate.
How Polarity Becomes
Welding involves the generation of spark or arc between the electrodes and the metals that are being fused. So to create a spark, the welding machines should, therefore, need electricity and electricity is available either in AC or DC. Most arc welders have AC/DC polarities so you have a choice when you need any of these. But how would you know when to use AC or DC in your welding?
Take note that DC, as we have mentioned, can provide electricity in a smaller amount while AC is the opposite. AC can cover a large area without diminishing its power while DC has its limits. AC is also hotter so with these, you can have an idea when you need to switch to DC to AC polarity. But to give you a good tip, to know when to use DC or AC on your welding project, always check the electrode you need to use and you will see there along with other letters and numbers are AC or DC.
If you want to know the parameters for certain types of wire or electrode, you can see on the machine’s door inside the right amperage, voltage and wire speed requirement. So we hope these tips could help you.
AC Vs DC Welding
In ac vs dc welding, DC welding is seen to be more flexible than AC welding and you can use both the electropositive and electronegative polarities and can still deliver a consistent flow of current. It can also maintain a more stable arc and easier to handle. With DC arc welders like the MIGs, once you shift from DC to AC, the machines can be capable of welding thinner metals.
Generally good on stick welding applications.
Best choice for vertical and overhead welding.
Best for TIG welding stainless steel.
Can MIG weld thinner metals on DC negative or DC positive polarities.
Best used for single carbon brazing, stick welding, hard facing, stainless steel welding, and cutting tap.
Arc blow is the usual problem when using gas shielding. Also termed as “arc wander”, arc blow is the deflection or distortion of the arc which is usually caused by magnetic field coming from the magnetized base metal or from the inconsistent flow of current or even by strong draft.
Welders running on DC require internal transformers in switching to AC making the units more costly.
DC welding will not work efficiently for aluminum because DC cannot produce the required heat needed to oxidize and blow away the oxide on the surface of the metal.
DC power is not supplied by electrical companies so you will need a separate transformer installed in your home which makes DC welding expensive to use
DC Vs AC Welding
When it comes to power distribution, AC has more power so you commonly find this current among high voltage equipment and devices. But when it comes to ac dc welding, this is only the second option for welding and the cheaper, entry-level AC-powered welders are usually more preferred by hobbyists and homeowners. So in essence there are also a lot of positive things that we can derive from AC welding.
Best choice for TIG welding aluminum as AC can provide more heat. Aluminum surfaces are usually protected by oxide film and once you switch your machine to electrode positive, this helps eliminate the oxide and at the same time cleaning out the metal surface.
Can manage blow arc effectively even with magnetized metals.
Used on metals where deep weld penetration is required especially of metal plates.
It provides fast filling of the molten electrode as it gives out stronger current and hotter arc.
Good choice in repairing machinery that normally has a magnetic field.
Can deal rusty metal surfaces better.
The welding result can be rougher compared to DC welding.
Can produce more spatter.
The arc can be difficult to maintain unlike with DC welding that has a steady flow of current.
DC Vs AC Welding
Here are the most distinctive features that you also must know when it comes to dc vs ac welding, from DC and AC welder features up to their prices:
Size. AC welders are much smaller than the DC welders.
Weight. AC welders are usually lighter than DC welders.
Arc blow. AC welding can deal better with arc blow while in DC welding this can be tedious to manage.
Voltage. AC welders are more versatile when it comes to wider coverage because electricity can travel fast without dropping its power, unlike DC welders.
Price. AC welders are usually for home and personal use including the beginner welders and these are generally cheaper than the DC welders.
So there you have it, the facts that you should know about the ac dc welding, their differences, strengths and weaknesses, and also when you should use each.
AC and DC welding, even though they have differences, can be used in many different tasks. And though we can now see that DC welding is more favored in many aspects because of its versatility and usefulness, AC welding can also be a good option in cases where DC welding is not advisable to use.
As we have discussed ac vs dc welding, you must remember that the most important thing in welding is always achieving deeper penetrations with your weld, producing a good bead and tough weld and how you can deal with any type of metal. So your success as a welder is not only based on what you should know about DC and AC welding but also what to do when faced with complicated welding tasks.
Interested to know the best welders for beginners? We also have a blog for you about this topic and you will learn a lot about what features you should look at to get your money’s worth.