Easy Filler Rod Selection for TIG welding Carbon Steel
Filler metal often gets overlooked in TIG welding carbon steel. The focus usually goes to tungsten, machine settings, or gas coverage — and those are all critical. But choosing the right filler rod and learning how to feed it smoothly does make a difference.
The main thing that some people skip over is....
Choose a TIG Welding Rod and NOT a Gas welding rod....Because they often look alike.
Gas welding rods are usually labeled RG45 or RG65 on the packaging but are often not labeled at all on the actual filler rod.
Gas welding rods are typically copper coated and look almost the same as TIG rods.
But they are not the same at all and gas welding rods will cause all sorts of porosity and other issues if you try to use them for tig welding.
The good news is there are really only 2 main filler rods to pick from when it comes to TIG welding plain carbon steel.
ER70S-2 and ER70S-6 are the main 2 TIG rods.
In this video, we’ll cover the differences between ER70S-2 and ER70S-6 filler rods
🧪 Why filler metal matters in TIG welding
The filler rod becomes part of your finished weld. Its chemistry, cleanliness, and how you introduce it into the puddle all affect:
- Weld appearance
- Strength and ductility
- Porosity and contamination
- How well the weld hammers, grinds, sands, or etches
Choosing the right rod for the job — and using it correctly — is just as important as dialing in your amperage.
🧲 ER70S-2 vs. ER70S-6: What’s the difference?
Both of these rods are commonly used for welding carbon and mild steels. They’re both designed to meet the “ER70” spec — 70,000 psi tensile strength. But they’re not exactly the same.
- Deoxidizers: Aluminum, titanium, zirconium
- Strengths: Excellent for general TIG welding on carbon steel that has been cleaned, or where fit-up isn’t perfect
- Where it shines: Root passes with a wide gap, tubing, repair work, small parts
- Typical look: Clean, fluid puddle with good wet-out
ER70S-2 is often the go-to for general TIG welding because it’s forgiving, versatile and readily available.
🔹 ER70S-6 – The MIG Standard (but also TIG-compatible)
- Deoxidizers: High silicon and manganese
- Strengths: Good for welding over light mill scale like you find on cold rolled steel or square tubing.
- Where it shines: open roots with tight gaps, and full penetration butt welds on sheet metal
- Typical look: Slightly more fluid puddle with a slightly glossier bead
✋ Filler feeding: Get your hands in sync
Even with the right rod, you need to feed it cleanly into the puddle. Here's how to build the skill of feeding the filler rod:
It might sound counter intuitive but padding beads on aluminum is a great way to learn to feed the filler rod even for carbon steel.
I call this the “the aluminum drill”
Essentially, this is stacking bead after bead on a piece of 1/8” or 3/16” thick aluminum.
Since aluminum requires much more filler wire feeding than steels, padding beads on aluminum is an efficient and cost effective training drill that will rapidly improve your filler wire feeding skills.
