TIG welding is one of the most versatile welding processes you can apply in a wide variety of metals and materials. One of the best uses of TIG welding is the ability to weld aluminum. But for perfect welding, you need to know what polarity is for TIG welding aluminum.
For TIG welding aluminum, the polarity must be reversed from the conventional AC current. Instead of using positively charged DC to make the arc, use negative DC to draw the arc away from the workpiece. This is referred to as reverse or negative polarity TIG, and is the best way to weld aluminum.
I will discuss here in detail the polarity required for aluminum welding. The writing will help you weld aluminum perfectly.
Ideal Polarity For TIG Welding Aluminum:
Welding aluminum can be a tricky proposition. The difficulty arises from the need to combine two dissimilar metals, aluminum, and filler material. In the past, the most common method for welding aluminum was MIG welding. However, it has a lot of limitations to welding aluminum, including the difficulty of starting a joint and the inability to weld on tight angles.
For TIG welding aluminum, you need to set the machine to AC. The TIG torch connection will be the same as steel, which is DCEN (electrode negative) or negative connection of your welder. All you have to do is change the AC / DC switch to AC. You may return to DC in the same way for steel weld.
When you cast aluminum using AC, it gives you more or less AC + by changing the sine wave. When electrons flow from +, the AC + time is shorter and more heat is transferred from the torch to the workpiece. This is good for penetration and convenient for your tungsten electrodes.
AC + Time On gives you 30% or more cleaning, which is good for thin sheets. You can combine it with a pulse to make it easier on a thin aluminum sheet. This will make your electrode more forceful.
So leave the TIG torch where it is usually the DCEN electrode negative to recap AC for aluminum. Low AC+ balance provides less than 20% on time for good penetration. In addition, a high balance ensures 30% for a better cleaning of a thin aluminum sheet.
5 Steps To Check Polarity For TIG Welding Aluminum:
To weld aluminum with TIG, it is important to check out the polarity. Here are the basic 5 steps, by following which you can check the polarity.
Step-1: Place The Base Metal
You can figure out the polarity by applying carbon or metal electrodes. For carbon electrodes, you require cleaning the base metal. Place the base metal in such a way that it is flat. Then shape the point of the two carbon electrodes by gently tapping, moving about 3 inches from the tip of the pressure. Your electrodes must be exact.
Step-2: Set The Amerate
Set the framerate from 135 to 150, regulate to anyone polar. Then apply a pressure that you hold for a short time. Change the length of the pressure from short to long as it allows you to identify the action of the pressure.
Step-3: Check The Pressure
If the polarity is negative, your pressure will stabilize. You find it is obvious to maintain, conical and uniform. If the polarity is positive, it will be confusing to maintain the pressure by depositing carbon in the base metal.
Step-4: Change The Polarity
Now change the polarity. Hit one pressure for the same length as the alternative electrode, and study the action of pressure again. The electrode worked with the negative polarity will burn evenly, and the other will quickly blunt and burn the tip.
Step-5: Notice The Sound
When you are working with the correct polarity, you hear a crackling sound. The wrong polarity will create a noise that will be popping and irregular. Getting an accurate polarity may require a lot of effort. The practice will help you identify the correct TIG polarity right now.
Electrode Polarity Chart Of TIG Welding:
You need to understand the polarity to know how much electric current is being generated by the equipment, and how much is being transmitted through the electrodes. Select the right electrode for the required polarity to ensure strong welding.
Because of polarity, electric current supplies positive and negative poles. Direct current streams in one way with a steady polarity. When welding TIG using DC, you have two options. But there is only one option for AC.
With AC, the current flows in one direction for half the time, then for the rest of the time. With a 60-Hz current, the AC changes its polarity 120 times per second.
The correct polarity creates a favorable environment for proper penetration when used with any metal electrode. Adding the wrong polarity will cause problems with spatter, minimal penetration, and controlling your stress. Quick burnout of electrodes and overheating are common problems with incorrect polarity.
The best TIG welder brands are marked to set the terminals. In these, you will find a switch that will allow you to change the polarity.
For your convenience, I am presenting a polarity chart below.
| Electrode | DC | AC | Position | Penetration | Usage |
| 6010 | EP | — | All | Deep | Min. Prep, Rough, High Spatter |
| 6011 | EP | Y | All | Deep | Min. Prep, Rough, High Spatter |
| 6013 | EP, EN | Y | All | Low | general |
| 7014 | EP, EN | Y | All | Med. | Smooth, Easy, Fast |
| 7018 | EP | Y | All | Low | Low Hydrogen, Strong |
| 7018AC | EP | Y | All | Low | Low Hydrogen, Strong |
| Ni-Cl | EP | Y | All | Low | Cast Iron |
| 308L | EP | Y | All | Low | Stainless |
3 Major Challenges Of TIG Welding Aluminum In AC:
TIG aluminum welding with AC brings many challenges. Of which notable 3 are:
1. Oxidation
Aluminum is a sensitive metal. By interacting with oxygen, the metal is at risk for oxidation or rust. Corrosion makes aluminum brittle and unsuitable for any application except welding.
2. Sensitive
Aluminum can be easily contaminated with impurities. It can exacerbate the problem when the metal comes in contact with air and dirt during casting. The quality and appearance of welding can change irreversibly when exposed to hydrogen or oxygen in the air.
3. Tendency To Be Perforated
When aluminum is heated, it absorbs hydrogen from the air and forms small bubbles in the molten weld pool. These parts are porous and weak, which affects the integrity of the joint.
Tips To Weld TIG Aluminum In AC:
TIG welding requires huge skill and experience to master as it is one of the leading welding techniques. It is also used to weld highly alloyed materials. Some tips can aid you in ensuring ideal welding.
- Place a heat sink next to the weld to ensure proper heat transfer. For TIG welders and molten weld pools, it ensures heat transfer and good penetration of pressure.
- Impurities in metals can seriously affect the quality of welding. So keep the aluminum clean.
- Preheating can play a very important role in ensuring a smooth joint. Hence, always preheat the aluminum before welding.
- Choose the right tungsten based on the ingredients. This is because TIG welding relies primarily on tungsten rods.
- Always keep the settings under control to prevent any errors.
Frequently Asked Question
Is It A Good Idea To Reverse Polarity When Welding Aluminum?
Alternative current (AC) is always recommended for welding aluminum. Reverse polarity is easier to create in AC welding. That is why the welding task has become much easier and more efficient.
During the welding process, an electrode with a positive polarity is used to weld with a negative workpiece. Through polarity reversal, aluminum oxide on its surface is broken down and allowing welding to be much easier.
Which Is The Correct Rod For Aluminum TIG Welding?
First, the quality of TIG welding depends largely on the tungsten rod. Therefore, you need to select the rod according to your needs. Tungsten rods are coded with different colors based on the components. These simplify the rod picking process.
The most commonly used filler rods for aluminum welding are 4043 and 5356. These rods are more tolerant in terms of various weld parameters, such as shrinkage, cracking, flexibility, flow, etc. The rods give better puddle control and you can use a wide variety of base alloys.
Can You Weld A Thick Aluminum TIG In AC?
Indeed, TIG in AC may not be convenient for casting coarse aluminum. But you can weld it if you wish. The thing that is most needed for this is experience. Multiple passes are a way to conquer coarse metal.
A welder should be able to calculate the thickness of the metal to cast it accurately and precisely. This will allow him to use the correct method of casting. First, bevel the edges and place a key bead before adding filler metal. You need to do filler and cap passes several times to get a strong joint.
Final Verdict
The TIG welding process uses a non-continuous arc to join metal. TIG welding aluminum comes in two forms: hard and soft. Most experts recommend hard TIG welding aluminum accomplished by reverse polarity, besides, soft is with direct current.
In this article, I have explained what polarity is for TIG welding aluminum. I have also discussed many important facts related to aluminum welding. Hope this writing helps you.
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