Two of the setup variables you must get right when TIG welding involves the choice of filler material and the tungsten electrode in your torch.
Both topics are substantial, so let’s focus on the filler material first (tungsten electrodes are covered here).
With TIG welding, you feed the puddle with filler material using a handheld rod. But these “rods” come in different sizes and compositions.
Knowing which filler rod to use, and when, makes your welds strong and aesthetically pleasing.
But with thousands of products on the market, even experienced welders struggle at times to find the right filler rod.
So, for your quick reference, below I have compiled answers to the most common questions and guidelines to finding the right filler rod.
Do I Need a Filler Rod?
Yes, you probably do need a filler rod. But you can fusion weld with a TIG welder without a filler rod.
But it is limited to welds where:
- The butt joint between the two pieces of metal has no gaps.
- The base metal is on the thicker side (e.g., 1/8 inch or thicker).
- You need more heat to fuse the metal (which risks burn-throughs).
- Strength is not important (fusion welds are weaker and are typically only used to tack pieces together).
This list also highlights the reasons that the majority of TIG welds incorporate a filler rod.
Filler Rod Basics
This filler material is a metal alloy specifically designed to withstand the high heat of welds and to fuse the two pieces of stock together as a composite.
So, not surprisingly, the alloy and size of filler rods vary for the varying stock thicknesses and types of base metals people weld.
TIG filler rods typically come in 3-foot lengths, packed in 10 or 50-pound boxes (or tubes). The diameter usually ranges from 1/16 to 1/4 inch.
The filler rods are also made with several alloys to handle different metals.
Since the TIG filler rod composition needed is often the same as that used for MIG filler material, some of the MIG wires are also sold for TIG welding. These are identified as “TIG cut lengths.”
Choosing a Filler Rod
Unfortunately, there is no definitive answer for the filler rod you “must” use for a weld. However, the weld you need to make defines certain parameters.
This criterion can then be used to follow certain guidelines. Also, manufacturers usually have detailed charts to help select a filler rod.
In general, the important parameters include the base metal thickness, its composition, and the type of weld joint (butt vs. fillet).
Using this criterion, you can use certain guidelines to zero in on the filler rod alloys and diameters you might want to use.
Filler Rod Alloys (“Composition”)
The American Welding Society (“AWS”) has categorized the various alloys and assigned special AWS “ER” numbers to more easily identify them.
Each number represents a “recipe” of chemical additives in the filler metal to address specific base metals and weld conditions.
The number of alloys available can be overwhelming.
Below you can find some simple guidelines to help you zero in on some common compositions of the filler rod.
Also, manufacturers often have charts you can consult to find their best product for a given weld.
Steel
- ER70S-2, ER70S-6, and several other ER70S-series options with different digits at the end to address specific conditions of the metal (e.g., dirty or clean) or the type of joint being welded.
- ER70S-6 is generally used for mild steel welding.
- For most types of mild steel
- Highly durable
- Highly fluid
- Highly resistant to corrosion
- 1/16-inch TIG filler
Stainless Steel
- ER308 & ER308L: One of the most common welding rods. It’s the choice for TIG welding 304 stainless steel, which is widely used in manufacturing. In addition, this filler rod alloy is used with 200-series and other 300-series stainless steels.
- ER309 & ER309L: Used for welding dissimilar metals. It can handle higher heat and has good corrosion resistance.
- ER316 & ER316L: Commonly used for pressure vessels, valves, chemical equipment, and marine applications. (The “L” refers to extra low carbon in the rod, less than 0.08%, which adds corrosion resistance.)
The numbers above are some of the more popular, but the roster of stainless steel base metals manufactured today is vast.
Also read: Can you weld stainless steel?
Aluminum
- ER4043: is a good general filler material for most aluminum applications. However, welding of 2xxx and 7xxx series aluminum is generally not recommended.
- ER5356: is used for 5xxx series aluminum and is generally preferred if the finished piece will be anodized.
- For most types of aluminum alloys
- Contains 5% silicon
- Improved fluidity
- Highly resistant to corrosion
- 1/16-inch TIG filler
Chrome Moly Tubing
- ER70S-2: is highly recommended for welding 4130 chrome-moly tubing in many applications.
- ER80S-D2: is recommended for welding 4130 chrome-moly tubing if a higher strength, less ductile weld is required.
- If your weld will be heat treated to obtain optimum strength, then use a filler metal that matches the chemistry of your tubing. Neither the 70S-2 nor 80S-D2 rods work in this instance.
Titanium
When welding titanium, you generally want to match the filler rod alloy to the base metal. Below are some of the common alloys you may run into:
- ERTi-2 – best for use with grade 2 titanium.
- ERTi-3 – best for use with grade 3 titanium.
- ERTi-5 – best for use with grade 5 titanium.
- ERTi-7 – same mechanical properties as ErTi-2 except with the addition of 0.12% palladium which imparts better corrosion resistance. Protects against crevice or under-deposit corrosion when ErTi-2 type Titanium wire is insufficient. ERTi-7 can be considered for welding Grade 2 or Grade 16.
- ERTi-9 and ERTi-9ELI – best for use with grade 9 titanium.
- ERTi-23 – best for use with grade 23 titanium.
Filler Rod Diameter
The thickness of the stock you TIG weld will suggest a filler rod diameter. There are all kinds of opinions on the right filler rod diameter.
Below I have assembled some guidelines to help you cut through the static.
- In general, use a filler rod with a diameter less than the thickness of the metal being welded.
- With a base metal thickness under 1/8 inch, the rod diameter should be slightly thinner than the metal being welded.
- For stainless sheet metal, use one size lower than you would use for carbon steel. This helps because you typically use less amperage on stainless steel thin stock, compared to carbon steel. At low amperage, a large rod chills the puddle and can cause an irregular bead.
- For aluminum, the same rules that you would use for steel sheet metal apply. In my experience, 1/16″ (1.6mm) wire can be used for sheet aluminum as thin as 0.040 inches.
- For thicker aluminum, sometimes the rod balls before it even reaches the puddle. If that happens, try a tighter arc and less torch angle. If that does not work, go up one size with your filler rod.
Also, there are numerous “calculators” online you can use.
They vary a little from one to another, but in general, they follow these guidelines in the table below for mild steel:
| Metal Thickness (inches) | Filler Rod Diameter (inches) |
|---|---|
| 1/16 | 0.045 or 1/16 |
| 3/32 | 1/16 or 3/32 |
| 1/8 | 1/16 or 3/32 |
| 3/16 | 1/8 |
| 1/4 | 3/16 |
| 1/2 | 1/4 |
Joint Type
Whether you are welding a butt or fillet joint may impact your TIG weld.
You will usually need more amps (i.e., heat) when welding a fillet joint.
Additional Considerations
Only use bare, uncoated rods designated for TIG welding.
Never use electrodes made for shielded metal arc welding (“SMAW”) stick welding.
Filler Rod Size & TIG Welder Settings
Assuming you have identified the right alloy for the base metal you want to weld, not only do you need to get the right diameter rod, you will need to “dial-in” your welder settings.
The amperage, gas flow, torch travel speed, and cup size vary, too.
The following guidelines provide you with good starting points for the filler rod diameter and welder settings.
But keep in mind you may need to tweak these settings depending on your welder and welding technique.
Check out these TIG tips and tricks if you’re struggling to with your TIG welds.
Stainless Steel
| Metal Gauge |
Joint Type |
Tungsten Size |
Filler Rod Size |
Cup Size |
Argon Gas Flow @ 20 PSI (CFH) |
Welding Amps |
|
|---|---|---|---|---|---|---|---|
| Travel Speed (IPM) |
|||||||
| 1/16″ (1.6mm) |
Butt | 1.6mm | 1.6mm | 4, 5, 6 | 11 (5.5) | 80 – 100 | 12″ |
| Fillet | 90 – 100 | 10″ | |||||
| 1/8″ (3.2mm) |
Butt | 1.6mm | 2.4mm | 4, 5, 6 | 11 (5.5) | 120 – 140 | 12″ |
| Fillet | 130 – 150 | 10″ | |||||
| 3/16″ (4.8mm) |
Butt | 2.4mm | 3.2mm | 5, 6, 7 | 13 (6) | 200 – 250 | 12″ |
| Fillet | 2.4mm, 3.2mm | 225 – 275 | 10″ | ||||
| 1/4″ (6.4mm) |
Butt | 3.2mm | 4.8mm | 8, 10 | 13 (6) | 275 – 350 | 10″ |
| Fillet | 300 – 375 | 8″ |
Low and Mild Carbon Steel
| Metal Gauge |
Joint Type |
Tungsten Size |
Filler Rod Size |
Cup Size |
Argon Gas Flow @ 20 PSI (CFH) |
||
|---|---|---|---|---|---|---|---|
| Welding Amps |
Travel Speed (IPM) |
||||||
| 1/16″ (1.6mm) |
Butt | 1.6mm | 1.6mm | 4, 5, 6 | 15 (7) | 95 – 135 | 15″ |
| Fillet | 95 – 135 | 15″ | |||||
| 1/8″ (3.2mm) |
Butt | 1.6mm / 2.4mm | 2.4mm | 4, 5, 6 | 15 (7) | 145 – 205 | 11″ |
| Fillet | 145 – 205 | 11″ | |||||
| 3/16″ (4.8mm) |
Butt | 2.4mm | 3.2mm | 7, 8 | 16 (6.5) | 210 – 260 | 10″ |
| Fillet | 210 – 260 | 10″ | |||||
| 1/4″ (6.4mm) |
Butt | 3.2mm | 4.0mm | 8, 10 | 18 (8.5) | 240 – 300 | 10″ |
| Fillet | 240 – 300 | 10″ |
Aluminum
| Metal Gauge |
Joint Type |
Tungsten Size |
Filler Rod Size |
Cup Size |
Argon Gas Flow @ 20 PSI (CFH) |
||
|---|---|---|---|---|---|---|---|
| Welding Amps |
Travel Speed (IPM) |
||||||
| 1/16″ (1.6mm) |
Butt | 1.6mm | 1.6mm | 4, 5, 6 | 15 (7) | 60 – 80 | 12″ |
| Fillet | 70 – 90 | 10″ | |||||
| 1/8″ (3.2mm) |
Butt | 2.4mm | 2.4mm, 3.2mm |
6, 7 | 17 (8) | 125 – 145 | 12″ |
| Fillet | 2.4mm, 1.6mm |
140 – 160 | 10″ | ||||
| 3/16″ (4.8mm) |
Butt | 3.2mm | 3.2mm | 7, 8 | 21 (10) | 195 – 220 | 11″ |
| Fillet | 210 – 240 | 9″ | |||||
| 1/4″ (6.4mm) |
Butt | 4.8mm | 3.2mm | 8, 10 | 25 (12) | 260 – 300 | 10″ |
| Fillet | 280 – 320 | 8″ |
Titanium
| Metal Gauge |
Joint Type |
Tungsten Size |
Filler Rod Size |
Cup Size |
Argon Gas Flow @ 20 PSI (CFH) |
||
|---|---|---|---|---|---|---|---|
| Welding Amps |
Travel Speed (IPM) |
||||||
| 1/16″ (1.6mm) |
Butt | 1.6mm | None | 4, 5, 6 | 15 (7) | 90 – 110 | 10″ |
| Fillet | 110 – 150 | 8″ | |||||
| 1/8″ (3.2mm) |
Butt | 2.4mm | 1.6mm | 5, 6, 7 | 17 (8) | 190 – 220 | 9″ |
| Fillet | 210 – 250 | 7″ | |||||
| 3/16″ (4.8mm) |
Butt | 2.4mm | 3.2mm | 6, 7, 8 | 21 (10) | 220 – 250 | 8″ |
| Fillet | 240 – 280 | 7″ | |||||
| 1/4″ (6.4mm) |
Butt | 3.2mm | 3.2mm | 8, 10 | 25 (12) | 275 – 310 | 8″ |
| Fillet | 290 – 340 | 7″ |
Conclusion
Choosing a TIG filler rod depends on a number of variables. The base metal composition, joint type, stock thickness, cleanliness of the stock, and thermal properties of the metal can all play into your selection.
It can be confusing at times.
But by using the guidelines in this article and, if needed, some information from the filler rod manufacturers, you can zero in on a good choice.
Of course, with experience, you will get more comfortable with the filler rods that work best with your TIG welder and your welding technique.
Also, be sure to determine the correct current (amperage) range for the rod. Plus, check the polarity, gas flow, cup size, torch speed, etc. before you strike an arc and start welding with a specific filler rod.
The process of selecting and using a filler rod feels overwhelming at times. But with experience and practice, it will become second nature.
It’s worth the effort since getting the variables right, including the filler rod, allows you to create strong, beautiful TIG welds on a consistent basis.