While your machine is not functioning properly up to the codes and standards of the industry, you need a quality weld finish. Choosing the best budget AC/DC Tig welder for the money is a challenging job. For this, one need to understand the difference between TIG (AC) and TIG (DC) welding.
TIG stands for Tungsten Inert Gas, also known as Gas Tungsten Arc Welding. TIG welding uses a tungsten electrode that has a very high melting point. TIG welding is the formulation of arc between the non-consumable tungsten electrode and the base metal. The Tungsten electrode is also known as a non-consumable electrode because it does not melt on heating. It becomes a part of the weld. The electrode becomes a filler in other welding processes.
The TIG torch is used to hold the tungsten electrode. The electrode is inserted in the collet that is used to adjust the length of the electrode by tightening or loosening up the end cap.
A constant electric power supply operates TIG welding. Most metals operate at DC current.
DIFFERENCE BETWEEN TIG (AC) WELDING AND TIG (DC) WELDIN
It is a common confusion that what exact difference between AC and DC Tig welding is. So, let's begin!
TIG (AC) WELDING
- AC is an alternating current that is the electrons flow back and forth, and there are two types of cycles: positive and negative cycles/polarities. Sixty cycles per second are used in the US and more than 50 Hz in Europe.
- AC TIG welding is used for aluminum and Magnesium. It can also be used for TIG brazing. It is not a preferred method for the stick method, but in case you need a cheap machine on which you can run a couple of different rods on AC, get a SWAM transformer machine.
- In AC, the electrons flow back and forth, and the whole cycle takes 1/60th of a second. If we divide the cycle into half, it would be 1/120th of a second. That means there are 120 direction changes per second.
- The AC knobs permit weld at high frequencies that are helpful for focus and stiffen the TIG Welding.
- There is no arc at direction changes.
- For TIG (AC) welding, there is probably the need to jack up heat and current to maintain the arc. Otherwise, it could stick.
- With the increase in frequency, the magnetic effect also increases, increasing the efficiency of transformers. The increase in frequency improves the arc stability and stiffens the arc making the welding conditions more controllable.
- Transformer, Transformer rectifiers, inverters, and engine drives are machines that are capable of AC. All transformers' rectifiers will do AC, but not but all inverters cannot do AC. It depends mainly on the machine.
- We have discussed before that aluminum is welded by TIG (AC) because aluminum has a problem with its melting point. Aluminum has two layers, i.e., the base aluminum and the oxide layer are formed when aluminum is exposed to air, and it has a very high melting point.
- The oxide layer has a melting point of 3600-degree Fahrenheit, while the base layer has 1200 degrees Fahrenheit. Before the base metal starts melting, the oxide layer must be cleaned off.
- TIG welding on AC is the best possible way to weld aluminum. Besides its low speed, the quality of the joint metal is excellent.
- AC is used for stick welding/arc welding because it is not affected by a magnetic field that the steel picks up over time when it is dragged through the Derby. Rod-like 7018 AC are specifically made to use on AC rather than DC, and it gives such a pretty looking weld.
TIG (DC) WELDING
- For DC current, the flow of electrons is in one direction. The polarity can either be positive or negative. DC TIG welding is the most preferred for most processes because of the continuous arc it creates.
- Stick usually is DC positive. Going through thinner metals can be DC negative.
- MIG welding will be DC positive for solid metals. Flux core is a little different.
- TIG welding, when in doubt, goes DC Negative. Aluminum and Magnesium are the exceptions. Otherwise, if steel or stainless nickel alloys or any other oddball metal like copper is DC negative.
- Flux core is usually DC positive with dual shield and DC Negative with self-shield.
- Welders doing self-shielding in-home projects use DC negative.
- While doing heavy duty with thick metals, that is dual shield welding, and it will probably be DC positive.
- Dc current is preferred for most of the welding.
- Machines that are capable of DC are anything, including Transformer rectifiers, inverters, and engine drives.
- While welding TIG (DC) and you think its perfect 90 amps or 100 amps here, but it is not. You get a little bit of wiggle in there.
Now there are two types of TIG (DC) welding.
- Direct Current Electrode Negative (DCEN)
- Direct Current Electrode Positive (DCEP)
Direct Current Electrode Negative (DCEN)
If you connect the electrode to the negative side of the circuit, 60 to 70 percent of the heat goes directly into the arc's positive side, resulting in a shallow penetration.
It is helpful while welding thin tubing.
Direct Current Electrode Positive (DCEP)
DC electrode positive is the most common way to run welds.
When you have a welding arc on the negative side, the electrons leave and end up on the positive side. Along with that, you end up taking about 60 70 percent of your heat to the positive side. The heat goes into the rod, and the rod melts off, sending metal back into the work piece, so the metal going into the work piece takes the heat back in there with it, so you get both, and it balances out between the two. At the electrode positive, the heat gets there and deeper penetration.
ADVANTAGES OF AC WELDERS
- AC has alternating polarities, and it is commonly used for welding thick metals and metals with a very high melting point. It is used for long seam welds.
- AC welding has a heavy spatter.
- It is preferred for Aluminum TIG, fast-fill, and down-hand heavy plate.
- AC welding is widely used for industrial repairs.
- AC welding is different because it can be used with metals that have a magnetic field.
- AC is not susceptible to arc welding, and it comes in handy, especially for repairing heavy machinery.
- AC welding is a great way to make fixes at home, automotive parts, and small fix appliances.
- There is less maintenance cost of AC power supply by the transformer.
- It is convenient to weld heavy metal plates in both down held and horizontally flat positions.
DISADVANTAGES OF TIG (AC) WELDING
- As compared to DC welding, more spatter is generated by AC welders, and it is the resultant of fluctuating polarity. And hence more time is spent on grinding off spatter.
- Unstable arc is the con for AC welders as the current keeps fluctuating back and forth, and it creates a break in welding.
- It is not suitable to weld most stick welding applications.
- AC welders cannot weld Non-ferrous materials.
- It is limited to coated materials only, and due to the continuous change of current position, it is unable to weld all electrodes.
ADVANTAGES OF DC WELDING
- DC has a single polarity that might be positive or negative.
- It has material diversity enabling it to weld all types of materials.
- It has most welding applications like overhead or vertical, for cutting tap or stainless TIG welding.
- DC welding is solid and smooth.
- It is preferred for the constant and stable arc.
- DC welding is preferred for places where the welds are observable, like furniture, tools, and vehicles.
- DC welding holds firm for an extended period, and the weld looks clean.
- AC welding is restricted to ferrous materials, but DC welding can be used on ferrous and non-ferrous materials.
- DC welders can weld vertically over the material, enabling them to weld on overhead positions.
- Due to constant power supply and generate minor spatter.
- It is suitable to weld all types of stick welding applications.
- DC welding is best for welding thinner materials.
- It provides a higher deposition rate.
DISADVANTAGES OF TIG (DC) WELDERS
- An internal transformer is needed to convert AC current into DC current as DC current is not supplied to electrical grid.
- DC welding is costly.
- Arc blowing is most probable DC welding because the magnetic current pulls the arc out of alignment with electrodes.
- Aluminum cannot be adequately welded by DC welding.
- There is more power consumption in DC welding.
For tidy-looking welds, TIG welding is the best choice. There are many best budget AC/DC TIG welders available in the market. All you need to understand is what material you are dealing with. For TIG welding, AC welding is the best, especially for aluminum with an oxide layer and higher melting point. It is less costly as compared to DC welding. DC has its benefits and is the best for stainless steel and thinner materials. Most TIG welding works best with DC supply.