Right TIG Filler Rods For Different Metals

TIG welding is considered one of the most challenging welding methods to master simply because there are a lot of things that can go wrong and ruin your welding. TIG filler rods are one of the parts of the puzzle known as GTAW or TIG welding that can make or break your project.

Choosing the right TIG filler rods for different metals is crucial in creating the strongest TIG welds, but many need help to make the right choice with the vast selection available. American Welding Society classified the TIG welding filler rods to make the selection more manageable, and we'll explain everything closely.

TIG Welding With Filler Rod

TIG welding is one of the few methods that can be performed without a filler rod. Welders rarely use filler metal when welding thin and delicate metals with little to no gaps between them. The heat of non-consumable tungsten electrodes and the TIG welding torch is high enough to melt and fuse two pieces. This is known as the autogenous welding process, or TIG welding without filler rods.

However, bevels and grooves are used to prepare the base materials for your hobby, DIY, and everyday welding projects. With the larger gap between the two pieces, you will need to deposit extra material to ensure the strength and penetration of a weld.

So, do you need a filler rod when TIG welding? Most likely, yes. If you are welding medium-thickness metal with a bevel, groove, or root, you will need the additional metal to provide strength and durability to the welded structure. Using gas welding rods or coat hanger wire can cause porosity and poor results, so we will closely explain everything you need to know about TIG filler rods and how to make the right choice.

TIG Filler Rods Explained

A TIG filler rod is a special metal alloy that withstands high heat and does not lose its characteristics after melting and solidifying. The primary role of TIG rods is to add the additional metal to the weld joint and help fuse the two pieces, creating high-quality welds with a desirable strength.

A TIG welding rod is similar to a MIG wire, and they share the composition. However, there are various types of TIG filler metals, and they differ on the:

• Composition (Type)
• Diameter
• Length

Choosing the suitable TIG filler metal will depend on the type and thickness of the metal you are welding. As a rule of thumb, you want the rod to have the same composition as the base metal and one size smaller than the metal thickness, but let's explore this further.

TIG Filler Rod Types For Various Metals

To help welders make an informed choice when choosing the right tig filler metal, AWS (American Welding Society) created a classification. The system for identifying the electrode classifications follows the standard pattern used in other AWS filler metal specifications.

As an example, we will use the most common TIG filler for mild steel - ER70S-6:

• The letters "ER" indicate that the filler metal may be used either as an electrode or a rod
• The number 70 indicates the required minimum tensile strength of 70,000 psi
• The letter "S" designates a solid electrode or rod ("C" represents a composite electrode)
• The suffix following the hyphen "6" indicates the chemical composition of the filler rod.

The AWS classification categorizes TIG rods for carbon steel (mild steel), low alloy, stainless steel, aluminum, nickel, copper, cast steel, titanium, zirconium, and copper. They are part of the same classifications as GMAW (Gas Metal Arc Welding) and PAW (Plasma Arc Welding) fillers, as they share the same properties and composition.

TIG Rods For Mild Steel Welding

As a hobbyist or a beginner, you are likely to TIG weld mild steel, even though TIG is often preferred for exotic or delicate metals. Mild steel is a carbon steel variant made from iron and less than 0.2% carbon. TIG filler rods for mild steel are categorized by the AWS A5.18 classification, which includes seven solid rods and seven composite TIG rods for carbon steel.

However, most of your projects and TIG welding on carbon steel and low-alloy steels will include using two types: ER70S-2 and ER70S-6 TIG filler rods. These are the two most popular steel welding rods with minimal differences in chemical composition.

• ER70S-2 is the most popular TIG rod for welding carbon and low alloy steels. This filler contains deoxidizers like titanium, zirconium, and aluminum. These deoxidizers are helpful when welding over dirty metals and surface contaminants. Theoretically, it can handle rusty metal, but you will sacrifice some weld quality.
• ER70S-6 is the most popular bare MIG wire, but it is often sold in cut lengths and used for TIG welding. This rod contains higher levels of manganese and silicon, which increases the weld pool fluidity and creates a ductile weld. This is great for sheet metal welding as it produces smooth-looking beads, ideal for construction work, farm implement fabrication, shaft buildup, tanks, truck bodies, etc.

• ER70S-3 is an alternative general-purpose rod suitable for carbon steels and other applications. It is a silicon and manganese deoxidized wire, making it excellent for general fabrication.

Stainless Steel Filler Rods

Stainless steel is an iron alloy containing at least 10.5% chromium, less than 1.2% carbon, and other alloying elements. Added chromium allows the iron to resist corrosion, which is crucial in many outdoor applications. Adding elements such as nickel, molybdenum, titanium, or niobium can further enhance these properties. However, alloying creates various grades of stainless steel, making choosing the right TIG filler metal challenging.

TIG welding stainless steel is another popular option, and the AWS A5.9 classification categorizes rods for stainless steel. There are various grades and classes of stainless steels, but for your home projects, you are likely to use ER308 and ER308L, ER309 and ER309L, or ER316 and ER316L.

• ER308 and ER308L are the go-to TIG fillers for stainless steel. They are compatible with the 200 and 300 series, including 304 stainless steel, the most commonly welded stainless steel grade. ER308L has the same analysis as type 308, except the carbon content has been held to a maximum of .03% to reduce the possibility of intergranular carbide precipitation. Typical applications include stainless steel fabrication of dairy, food, or restaurant equipment, chemical tanks, and general-purpose applications.

YesWelder ER308L 5LB Stainless Steel TIG Welding Rod

• ER309 and ER309L stainless steel filler rods are often used when welding dissimilar metals and stainless steel to carbon steel. ER309 will also weld hot rolled steel without porosity and make critical welds in the power generation industry.
• ER316 and ER1316L are low-carbon alloys primarily used for welding low-carbon molybdenum-bearing austenitic alloys. This rod produces a weld deposit with a pleasing bead appearance and exceptional crack resistance.

TIG Welding Rods For Aluminum

Aluminum is a lightweight silvery-white metal known for its good corrosion resistance, aesthetics, and light, making it widely used in various industries. However, aluminum can be hard to weld, so many turn to a TIG welder as a solution.

Similar to stainless steel, there are a number of aluminum grades, which can make choosing the suitable aluminum rod a challenging task, and the AWS A5.10 classification specifies all aluminum rods. Although there are dozens of fillers, you will likely use either ER4043 or ER5356 filler rods in your everyday aluminum applications.

• ER4043 is a general-purpose filler rod alloy containing 5% silicon addition and welding heat-treatable base alloys. Silicon addition improves the weld pool's fluidity and makes the welding less sensitive to cracking. The bright finish is a good choice for welders.

YesWelder ER4043 5LB Aluminum TIG Welding Rod

• ER5356 is a 5% magnesium aluminum rod used to weld 5000 series aluminum. The post-anodizing color tint is white, making it a good choice for anodizing applications. This rod has higher welding strength and better flexibility than ER4043.

TIG Filler Rods For Nickel Alloys

Nickel and nickel alloys are widely used due to their corrosion resistance, heat resistance, high-temperature properties, and low-temperature properties. Nickel alloys are prone to porosity, cracking, contamination, and oxide inclusions, so welding nickel requires proper welding technique and the right filler rod.

TIG filler rods for nickel alloys are categorized by AWS A5.14 classification, and they can be divided into several groups based on the alloying elements added to the nickel. Even though you are less likely to work with nickel as a hobbyist or home welder, here are some of the standard rods used in TIG welding:

• ERNi TIG filler rods are used when welding wrought and cast forms of commercially pure nickel. This filler rod contains titanium to control the porosity.
• ERNiCu are nickel-copper rods used to weld alloy 400, which is highly resistant to corrosion by alkaline solutions, non-oxidizing salts, and seawater.

• ERNiCr is the nickel-chromium TIG filler rod used for nickel-chromium-iron alloys, or surfacing steel with nickel-chromium-iron weld metal, for dissimilar welding of nickel-base alloys, and for joining steel to nickel-base.
• ERNiCrFe is the nickel-chromium-iron TIG welding rod used when welding nickel-chromium-iron alloys. The higher niobium content of the filler metal minimizes cracking where high welding stresses are encountered.
• ERNiFeCr is the nickel-iron-chromium TIG welding rod for welding the nickel-iron-chromium-molybdenum-copper alloys.
• ERNiMo rods are used for welding nickel-molybdenum alloys.

TIG Filler Rods For Titanium

Titanium is another lightweight but strong and corrosion-resistant material widely used in aircraft, spacecraft, shipbuilding, and many advanced industries. This material is highly resistant to chemical reactions and has the highest strength-to-weight ratio of any metal.

Welding titanium is often carried out by TIG welding, and it has similar weldability to stainless steel, even though it requires somewhat better cleanliness and protection. AWS classifies titanium TIG filler rods by the A5.16 classification.

The key to choosing the right filler rod for titanium is matching the filler rod grade with the titanium grade. For example, welding grade 5 titanium requires an ERTi-5 filler rod, welding grade 2 titanium requires an ERTi-2 rod, and vice versa.

TIG Filler Rods For Copper And Copper Alloys

Copper provides excellent electrical conductivity and corrosion resistance, which makes it widely used in industries across the globe. Copper pipes and fittings are often brazed or soldered, but copper and its alloys can also be welded by various methods, including TIG welding (GTAW).

Copper alloys are classified into nine groups, each with a respectable filler rod. The rods are presented in the AWS A5.7 classification, and here are the matching choices:

• ERCu are the filler rods designed for pure copper of a minimum 98% copper composition.
• ERCuSn is the filler rod designed for copper-tin or phosphor bronze alloys, and TIG welding uses ERCuSn-A, with about 5% tin.
• ERCuSi is the silicon-bronze or copper-silicon filler rod widely used in welding silicon bronze or copper-zinc alloys.
• ERCuAl is the iron-free aluminum bronze or copper-aluminum filler rod used for various aluminum bronze alloys.
• ERCuNi is the copper-nickel filler rod with roughly 70% copper and 30%, used to weld most copper-nickel alloys.

TIG Filler Metals For Magnesium Alloys

Magnesium and magnesium alloys are pretty similar to aluminum, and if you welded one, you will likely know how to weld the other. Magnesium also creates an oxide layer, presenting similar challenges when welding and achieving desirable mechanical properties and critical welds. Although several welding processes can be used for welding magnesium, the ideal method is Tungsten Inert Gas (TIG).

Magnesium is often combined with other materials to increase its strength and suitability for various applications. That's why there are various magnesium alloys, which can present issues when choosing the right filler rod. However, the four most commonly used filler metals to weld magnesium alloys are ER AZ61A, ER AZ101A, ER AZ92A, and ER EZ33A.

• AZ61A filler metal is generally preferred for welding wrought base metals of those alloys because of lower cracking tendency.
• AZ92A filler metal shows less crack sensitivity in welds made in cast Mg-Al-Zn and AM100A base metals
• AZ101A filler metal may also be used to weld those cast base metals.
• EZ33A filler metal is used for welding wrought and cast base metals designed for elevated-temperature service

Zirconium Filler Rods

Zirconium is another "exotic" metal you are less likely to encounter during your welding journey, but it can be TIG welded. It has a low coefficient of thermal expansion, which contributes to low distortion during welding, and there are classified TIG filler rods for it.

Zirconium is TIG welded with ERZr2, ERZr3, or ERZr4 rods.

• ERZr2 is a commercially pure zirconium rod,
• ERZr3 rod has tin as an alloying element. Tin increases the strength of the while retaining good ductility.
• ERZr4 rod contains columbium as an alloying element, producing good ductility with a tensile strength of at least 80 ksi.

Filler Rod Size And Length

Besides matching the composition of the base metal, choosing the suitable filler rod will vary on the thickness of the metal. While rods come in 3-foot lengths, packed in 5-10 or 50-pound tubes, the sizes will vary. TIG filler metals you will likely use will have a rod diameter of 0.045" up to 1/4".

As a rule of thumb, you will want to use a diameter rod one size smaller than the thickness of the base material. For example, 3/16" metal will require 1/8" rod. However, when welding thin metals up to 1/8", you can use 1/16 or 3/32" rod diameter. Here are some of the examples:

Final Thoughts

Making critical welds with TIG welding can be reasonably complex, from choosing the right TIG welder, preparing the welds, and practicing proper technique. Choosing the right filler is also one part of the equation, but making an informed choice is not always daunting.

Understanding the composition and types of TIG filler rods is crucial in achieving high-quality welds and everlasting results. Today, each rod must strictly follow the AWS specification, so matching the composition, especially after we explained how each rod affects the welds, shouldn’t be an issue for you.